The Use of Proxies

“Economists cannot directly measure the health of an economy; instead, they use various indicators or proxies like GDP growth rates, employment figures, inflation rates, and consumer spending.” This highlights the complexity of assessing economic health and the reliance on multiple data points to infer overall activity.
“SAT scores have long been used by colleges as a proxy for a student’s readiness for college-level work. However, critics argue that SAT scores are more strongly correlated with socioeconomic status than with college success.” This highlights the limitations and potential biases of using standardized test scores as proxies for academic potential, sparking debates on fairness in college admissions.
“Researchers use proxies like brain imaging techniques (fMRI, PET scans), physiological responses (heart rate, galvanic skin response), and behavior analysis to study and infer mental states and processes.” This illustrates the indirect methods used in psychology and neuroscience to understand complex cognitive and emotional states.

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Some phenomena cannot be scientifically evaluated directly and require that we use proxies to measure them. Give a list of 7 such cases across a wide variety of disciplines.

Climate Change Over Geological Time Scales
In climatology and geology, direct measurements of historical climate conditions are impossible due to the vast time scales involved. Scientists use proxies like ice cores, tree rings, and sediment layers to infer past climate conditions. These proxies can tell us about the Earth’s temperature, atmospheric composition, and even rainfall patterns thousands to millions of years ago.
Black Holes
In astrophysics, black holes themselves cannot be directly observed because their gravitational pull is so strong that not even light can escape. However, their presence is inferred through the behavior of nearby stars and gas. For example, if a star orbits around an invisible object or gas is heated as it spirals into a seemingly empty area of space, these can be indicators of a black hole.
Dark Matter and Dark Energy
In cosmology, dark matter and dark energy constitute most of the universe’s mass-energy content, yet neither can be directly observed with current technology. Their existence is inferred from gravitational effects on visible matter, cosmic microwave background radiation, and the universe’s large-scale structure.
Economic Health
Economists cannot directly measure the health of an economy; instead, they use various indicators or proxies like GDP growth rates, employment figures, inflation rates, and consumer spending to get a sense of overall economic activity and health.
Ancient Diets
In archaeology and paleontology, direct evidence of prehistoric diets is rare. Researchers use proxies such as stable isotope analysis of bone collagen, dental wear patterns, and remnants of plant material found in dental calculus to infer ancient dietary practices.
Subatomic Particles
In particle physics, many subatomic particles cannot be observed directly due to their extremely short lifespans and the indirect nature of their interactions. Scientists infer their existence and properties through particle accelerators, observing the outcomes of high-energy collisions and identifying the particles by the tracks they leave in detectors.
Human Cognition and Emotions
In psychology and neuroscience, direct observation of thoughts, cognition, and emotions is not possible. Researchers use proxies like brain imaging techniques (fMRI, PET scans), physiological responses (heart rate, galvanic skin response), and behavior analysis to study and infer mental states and processes.

That’s right! There are many phenomena that can’t be directly measured by science, so researchers use indirect methods to assess them. Here are 7 examples across different fields:

Animal intelligence: Animal behavior can be a good proxy for intelligence. For example, a crow’s ability to use tools to access food or a chimpanzee’s capacity to solve puzzles can hint at their cognitive abilities.
Past climate: Scientists use things like ice cores, tree rings, and ocean sediments to understand past climates. By analyzing the gases trapped in bubbles in ice cores or the thickness of growth rings in trees, researchers can piece together information about past temperatures and atmospheric conditions.
Human personality: Psychologists use surveys, questionnaires, and behavioral tests to assess personality traits like extroversion, agreeableness, and neuroticism. These tests provide indirect measures of a person’s underlying personality.
Economic well-being: Gross Domestic Product (GDP) is a common proxy for a country’s economic well-being. It represents the total market value of all final goods and services produced in a country in a given year. However, GDP doesn’t take into account factors like income inequality or environmental quality.
Black holes: Black holes themselves cannot be directly observed because they don’t emit light. However, astronomers can detect their presence by observing the gravitational effects they have on nearby objects.
Dark matter: Similar to black holes, dark matter is invisible and cannot be directly detected. Scientists infer its existence based on its gravitational influence on visible matter in the universe.
Consciousness: There is no single scientific definition or method for measuring consciousness. Scientists use brain imaging techniques and behavioral studies to try to understand the neural correlates of consciousness, but there is still much debate about what consciousness truly is and how to measure it.

Provide 5 actual cases in which a proxy was revealed to be improper.

Hockey Stick Graph Controversy
In the early 2000s, the “hockey stick” graph, which used tree rings as a proxy to reconstruct past temperatures, became a focal point of controversy in climate science. Critics argued that the methodology used to combine tree-ring data with other temperature proxies was flawed, potentially overestimating the rarity and severity of contemporary warming trends. Subsequent investigations highlighted the challenges of using tree-ring data as a proxy for temperature, especially in terms of accurately representing long-term temperature changes and the phenomenon known as “divergence,” where tree-ring widths do not correlate with temperature after a certain point.
Dow Jones Industrial Average (DJIA) as a Market Proxy
The DJIA is often used as a proxy for the overall health of the United States stock market and, by extension, the U.S. economy. However, because it includes only 30 large public companies, it has been criticized for not accurately reflecting the broader market or economy, especially as it omits companies in sectors like technology and biotech that have grown significantly in importance. This limitation became particularly evident during times of market stress or when the tech sector outperformed traditional industries, leading many to argue for the use of more comprehensive indexes like the S&P 500.
Body Mass Index (BMI) for Health and Obesity Measurement
BMI, calculated as weight in kilograms divided by the square of height in meters, is widely used as a proxy for body fat and overall health. However, it has been criticized for not distinguishing between fat and muscle mass, leading to misclassification of athletic individuals with a high muscle mass as overweight or obese, and failing to identify individuals with a normal weight but high body fat percentage as at risk. This misclassification has implications for healthcare advice and treatment, illustrating the limitations of BMI as a health proxy.
SAT Scores as College Readiness Indicators
SAT scores have long been used by colleges as a proxy for a student’s readiness for college-level work. However, critics argue that SAT scores are more strongly correlated with socioeconomic status than with college success, disadvantaging students from lower socioeconomic backgrounds. This critique has led to a growing movement among colleges to become test-optional or to place less emphasis on standardized tests in admissions processes, especially after studies suggested high school GPA might be a better predictor of college success.
GDP as a Measure of National Well-being
Gross Domestic Product (GDP) is commonly used as a proxy for a country’s economic well-being and progress. However, GDP has been criticized for not accounting for the distribution of income among residents of a country, the depletion of natural resources, or the value of non-market activities such as household labor and volunteer work. Furthermore, an increase in GDP does not necessarily mean an improvement in the quality of life for a country’s citizens, as evidenced by countries with high GDP growth but also high levels of inequality, pollution, and social discontent. This has led to the development of alternative measures, such as the Human Development Index (HDI) and Gross National Happiness (GNH), to provide a more holistic view of well-being.

Enron Shareholder Proxy Scandal (2001): Enron, an energy company, used misleading information and tactics to influence shareholder votes through proxy advisors. An investigation revealed the company pressured employees who held shares to vote with management, even if it wasn’t in their best interests. This exposed the flaws in proxy voting systems without proper oversight.
Voting Machine Errors (2000 US Election): During the infamous 2000 US presidential election, voting machines in Florida malfunctioned, leading to inaccurate vote counts. These machines were supposed to be a proxy for voters’ choices, but their failure undermined the integrity of the election.
SAT Scores and College Success (Ongoing): Standardized tests like the SAT were once considered a strong proxy for college readiness. However, studies have shown that factors like socioeconomic background and access to test prep resources often have a bigger influence on scores than actual academic ability. This raises questions about the fairness of using such tests as a sole admissions criterion.
Economic Inequality and GDP (Multiple): GDP, as mentioned earlier, is a common proxy for economic well-being. However, critics argue it doesn’t capture the distribution of wealth within a country. A high GDP could mask significant income inequality, where a small percentage of the population holds most of the wealth.
Animal Testing and Human Health (Ongoing): Animal testing has long been used as a proxy to predict the effects of drugs and treatments on humans. However, there are growing concerns about the limitations of this approach. Animal physiology can differ significantly from humans, leading to inaccurate or misleading results.

These are just a few examples, and the debate about appropriate proxies continues across many fields.

How might we assess when we can legitimately make a causal inference from a proxy to the target phenomenon?

Making a legitimate causal inference from a proxy to the target phenomenon involves several critical steps and considerations to ensure that the relationship between the proxy and the phenomenon is not merely correlative but indicative of a causal link. Here are key principles and methodologies that can aid in this assessment:

Strong Theoretical Foundation: There must be a well-founded theoretical basis for expecting that changes in the proxy are causally related to changes in the target phenomenon. This involves understanding the mechanisms through which the proxy influences the phenomenon and being able to articulate why this relationship holds.
Consistency Across Multiple Studies: Observing consistent results across different studies, contexts, and methodologies strengthens the argument for a causal relationship. Replicability of findings using the proxy in varied settings reduces the likelihood that observed relationships are due to chance or confounding variables.
Temporal Precedence: For a causal relationship to be considered, it is necessary to establish that changes in the proxy precede changes in the target phenomenon. This temporal ordering is critical to infer causality rather than a mere association.
Elimination of Confounding Variables: A robust causal inference requires that alternative explanations for the observed relationship between the proxy and the target phenomenon be systematically ruled out. This involves controlling for potential confounders that could otherwise explain the observed relationship.
Granger Causality Tests: In time-series analysis, Granger causality tests can be used to assess whether changes in one variable can predict changes in another variable, which is a prerequisite for causal inference. While not definitive proof of causality, these tests can provide evidence of temporal precedence and predictive power.
Instrumental Variable (IV) Analysis: IV analysis is a technique used in statistics and econometrics to estimate causal relationships when controlled experiments are not feasible. An instrumental variable is correlated with the proxy but not directly with the outcome, except through its effect on the proxy. This method helps to control for unobserved confounders.
Counterfactual Reasoning: Assessing what would have happened to the target phenomenon in the absence of changes in the proxy helps establish a causal link. While often theoretical, approaches like difference-in-differences and synthetic control methods can provide empirical counterfactuals.
Mediation Analysis: This involves identifying and testing the mechanism by which the proxy affects the target phenomenon. Demonstrating that the relationship between the proxy and the phenomenon is mediated by an expected process adds credibility to the causal claim.
Experimental Manipulation: Where possible, experimentally manipulating the proxy and observing the consequent effect on the target phenomenon provides strong evidence for causality. In many cases, however, such manipulation is not feasible due to ethical or logistical constraints.
Peer Review and Consensus: Finally, peer review and scientific consensus play a crucial role in assessing the legitimacy of causal inferences. The scrutiny of the scientific community can help identify flaws, biases, or alternative explanations that the original investigators may have overlooked.

In sum, making a legitimate causal inference from a proxy to the target phenomenon requires careful consideration of theoretical justifications, empirical evidence, and methodological rigor to ensure that the relationship is not spurious but indicative of a real causal connection.

Assessing causal inference from a proxy to the target phenomenon requires careful consideration of several factors:

Strength of the Association: A strong correlation between the proxy and the target variable is a good starting point. The stronger the association, the more likely it is that the proxy reflects the actual phenomenon.
Temporal Relationship: The proxy variable should ideally precede changes in the target variable. This helps establish that the proxy is influencing the target and not the other way around.
Ruling Out Alternative Explanations: It’s crucial to consider other factors that might influence both the proxy and the target variable. If there are alternative explanations for the observed association, then the causal inference from proxy to target is weakened.
Validity of the Proxy: A good proxy should accurately reflect the target phenomenon. If the proxy itself is flawed or doesn’t truly capture the essence of what you’re trying to measure, then any causal inferences will be unreliable.
Mechanistic Understanding: Ideally, there should be a plausible explanation for why the proxy influences the target variable. Understanding the underlying mechanism strengthens the case for causal inference.

Here’s a breakdown using the example of SAT scores and college success:

Strong Association?: There might be a correlation between high SAT scores and academic performance in college, but is it strong?
Temporal Relationship?: SAT scores are taken before college, so temporally they precede academic performance.
Alternative Explanations?: Socioeconomic background, access to preparatory resources, and non-cognitive skills can all influence both SAT scores and college success. Are these factors being accounted for?
Validity of Proxy?: Do SAT scores truly capture a student’s potential to succeed in college, or are they measuring something else entirely?
Mechanistic Understanding: How exactly do SAT scores translate into college success? Is there a clear mechanism at play?

By carefully examining these factors, researchers can make more informed judgments about the legitimacy of causal inferences drawn from proxies. In the case of SAT scores, the picture is complex, and there is ongoing debate about how much weight to give them in college admissions decisions.

Provide me with 5 examples of counter-intuitive or surprising legitimate proxies.

Pirate Activity as an Indicator of Economic Health in Maritime Regions: In some instances, the level of pirate activity in a region has been used as a surprising but legitimate proxy for local economic health and stability. The rationale is that piracy often declines in areas where economic conditions improve, as there are more legitimate opportunities for income, and security measures are likely to be stronger. Conversely, increased piracy can indicate economic desperation or a lack of effective governance, reflecting broader economic troubles.
Satellite Nighttime Lights for Economic Activity: The intensity of nighttime lights captured by satellites has been used as a proxy for economic activity within a region. This approach is based on the observation that more economically developed and active areas tend to produce more light pollution at night. This proxy has been particularly useful in assessing economic growth in regions where reliable economic data are scarce or unreliable.
Sewage Analysis for Drug Use in Communities: The analysis of sewage water for traces of drugs has emerged as a surprising but effective proxy for assessing the level of drug consumption within a community. This method can provide an objective measure of drug use patterns over time, unaffected by the biases and underreporting inherent in surveys and self-report methods. It can also reveal the emergence of new substances in the community.
Tree Growth Rings as Proxies for Historical Earthquakes: In dendrochronology, the study of tree rings for dating and studying past climates, tree growth anomalies have been used as proxies for historical earthquakes. Trees that undergo stress from ground shaking can show changes in growth patterns, such as narrowed rings, that coincide with known earthquakes or suggest previously undocumented seismic events. This method provides a novel way to extend the seismic record further back than instrumental records allow.
Ambulance Call-Outs as Indicators for Flu Outbreaks: In some regions, an increase in ambulance call-outs has been used as an early indicator of flu outbreaks or other public health emergencies. Before widespread testing or hospital admissions increase, a spike in calls related to respiratory distress can signal the beginning of an outbreak. This proxy is beneficial for early intervention and preparing healthcare services for increased demand, showcasing how emergency services data can provide unexpected insights into public health trends.

Coffee Prices and Global Shipwreck Rates: This might sound like a wacky connection, but there’s a surprising correlation. Coffee is a major global commodity, and its price fluctuates based on supply and demand. One factor affecting supply? Shipwrecks! Since a significant portion of coffee is transported by sea, a rise in coffee prices can sometimes be a counter-intuitive proxy for an increase in shipwrecks. This is because higher coffee prices incentivize riskier shipping practices, like overloading ships or taking less safe routes, which can lead to more accidents.
Lipstick Sales and Economic Downturns: Believe it or not, lipstick sales can sometimes be a counter-intuitive proxy for economic recessions. The theory goes that during economic hardship, people might cut back on expensive luxuries, but lipstick is a relatively inexpensive way for consumers, particularly women, to treat themselves and feel good. So, a surge in lipstick sales could ironically foreshadow an economic downturn.
Hemline Index and Stock Market Performance: This is a historical, and not entirely reliable, proxy, but it’s an interesting one nonetheless. The theory proposes a correlation between rising hemlines in women’s fashion and a booming stock market. The reasoning is that during periods of economic optimism, people feel more confident and carefree, which can be reflected in more revealing clothing styles. Conversely, falling hemlines might be seen as a proxy for economic conservatism and potentially a market downturn. However, this correlation is not always accurate and can be influenced by other fashion trends.
Spelling Bee Winners and Stock Market Crashes: This is another attention-grabbing, but not entirely reliable, proxy. A study proposed a statistical correlation between the number of winners in the Scripps National Spelling Bee and subsequent stock market crashes. The theory suggests that a high number of winners might indicate a focus on rote memorization over critical thinking skills, potentially reflecting a broader societal trend that could contribute to economic instability. However, the validity of this proxy is highly debated, and the study itself has been criticized for methodological flaws.
Number of Pirates and Global Temperature: This might seem like something out of a fantasy novel, but there’s a potential link. Studies suggest that periods of increased global piracy often coincided with cooler global temperatures. The reasoning is that cooler temperatures can disrupt major ocean currents, impacting weather patterns and making certain regions more difficult to navigate. This could create opportunities for pirates to exploit these disruptions and prey on vulnerable ships. While the correlation isn’t perfect, it highlights the unexpected ways in which seemingly unrelated phenomena can be connected.

Create a 10-item quiz on the discussion above.

Quiz

What is a common proxy used to reconstruct past climate conditions?
How are black holes detected in the universe?
What economic indicator is criticized for only including 30 large public companies?
Why is the Body Mass Index (BMI) considered an improper proxy for overall health?
Which standardized test has been questioned as a college readiness indicator due to its correlation with socioeconomic status?
What unconventional proxy has been used to assess the level of drug consumption within a community?
How is satellite nighttime light intensity used in economic studies?
What natural feature’s growth anomalies are used as proxies for historical earthquakes?
In what way can ambulance call-outs serve as a proxy for public health surveillance?
What is the primary challenge in using tree rings as a proxy for temperature reconstructions mentioned in the hockey stick graph controversy?

Answers

Ice cores, tree rings, and sediment layers.
By observing the behavior of nearby stars and gas.
Dow Jones Industrial Average (DJIA).
It does not distinguish between fat and muscle mass.
SAT scores.
Sewage analysis.
As a proxy for economic activity.
Tree growth rings.
Indicators for flu outbreaks or other public health emergencies.
The “divergence” problem, where tree-ring widths do not correlate with temperature after a certain point.

Quiz: Unveiling the Hidden: Using Proxies to Measure the Unseen

Read each question carefully and choose the best answer.

Why might scientists use proxies to study phenomena? a) Proxies are always more accurate than direct measurements. b) Some phenomena cannot be directly observed or measured. c) Proxies are a cheaper alternative to sophisticated equipment. d) All of the above
Which of the following is NOT a good example of a proxy in scientific research? a) Tree rings used to understand past climates b) Brain scans used to study consciousness c) GDP used to measure a country’s economic well-being
d) Observing a black hole’s gravitational effects to detect its presence
The Enron Shareholder Proxy Scandal of 2001 highlights a problem with using proxies. What was the main issue? a) Proxies were not readily available to all shareholders. b) The proxies used were outdated and inaccurate. c) The company manipulated the proxy voting system. d) Shareholders did not understand how to use proxies effectively.
When assessing a proxy’s validity, which factor is LEAST important? a) The strength of the correlation between the proxy and the target variable b) Whether the proxy precedes changes in the target variable c) The existence of alternative explanations for the observed association d) The popularity of the proxy among researchers in the field
Imagine a study finds a correlation between ice cream sales and shark attacks. Why might this be a poor proxy for shark behavior? a) Ice cream sales don’t directly influence shark behavior. b) People might eat more ice cream when they are already at the beach, increasing the likelihood of both activities. c) There might not be enough data on ice cream sales and shark attacks. d) All of the above
According to the passage, what makes a causal inference from a proxy more reliable? a) A weak association between the proxy and the target variable b) A clear understanding of the mechanism linking the proxy to the target c) The proxy being more expensive to measure than the target variable d) The proxy being a recent invention in scientific research
Why might lipstick sales sometimes increase during economic downturns? a) Lipstick is a durable good that people invest in during recessions. b) People have more disposable income to spend on luxuries during economic hardship. c) Lipstick sales are a reliable indicator of overall consumer spending. d) Lipstick is a relatively inexpensive way for consumers to treat themselves during tough times.
The Hemline Index theory suggests a connection between what two things? a) Rising sea levels and global fashion trends b) Stock market performance and the length of women’s skirts c) The invention of new fabrics and economic recessions d) Competition in the fashion industry and political elections
A study proposed a link between the number of winners in a spelling bee and stock market crashes. What is a potential weakness of this theory? a) Spelling bees are not a widespread phenomenon. b) Winning a spelling bee doesn’t necessarily indicate intelligence. c) The study might not have considered other factors affecting the stock market. d) All of the above
Cooler global temperatures might be a reason for what, according to the passage? a) An increase in the number of international trade agreements b) A decline in global piracy
c) A surge in investments in renewable energy sources d) A rise in the popularity of winter sports

Answer Key:

Provide 15 discussion questions relevant to the content above.

How do ice cores provide information about past climates, and what specific data can they reveal?
Discuss the implications of using black holes’ indirect effects on nearby stars and gas as evidence of their existence. How reliable are these observations?
Evaluate the effectiveness of the Dow Jones Industrial Average (DJIA) as a proxy for the overall health of the stock market and the U.S. economy. What are its limitations?
Body Mass Index (BMI) is widely used as a health indicator. Discuss why BMI might not be an accurate measure of an individual’s health status.
Reflect on the criticism of SAT scores as indicators of college readiness. How might reliance on SAT scores affect students from varied socioeconomic backgrounds?
Explore the ethical implications of using sewage analysis as a proxy for community drug use. What privacy concerns might arise?
Discuss the benefits and potential drawbacks of using satellite images of nighttime lights as indicators of economic activity.
How do tree growth anomalies serve as proxies for historical earthquakes? Discuss the reliability and limitations of this method.
Ambulance call-outs as an early indicator of flu outbreaks represent an innovative use of data. Discuss how this method could improve public health responses.
The “hockey stick” graph controversy highlights challenges in using proxies for climate change research. Discuss the importance of methodology and data interpretation in climate science.
Consider the role of proxies in scientific research. What criteria should be used to evaluate the validity of a proxy?
How can researchers ensure that a proxy is a legitimate and accurate representation of the target phenomenon?
Discuss the role of technological advancements in discovering new proxies for studying hard-to-measure phenomena.
Reflect on the importance of proxies in historical and archaeological research. How do proxies bridge the gap between the present and the past?
Evaluate the potential of using unconventional data sources, like ambulance call-outs or sewage analysis, in other areas of research. What other innovative proxies might be explored?

Discussion Questions: Unveiling the Hidden: Using Proxies to Measure the Unseen

Can you think of any other examples in your field of study (or everyday life) where proxies are used? How effective are they?
What are some of the ethical considerations involved in using proxies? Are there situations where using a proxy could be misleading?
The text mentions the limitations of GDP as a measure of economic well-being. What other factors do you think should be considered when evaluating a country’s economic health?
How can scientists improve the design of studies that rely on proxies to draw causal inferences?
The Enron Scandal demonstrates the potential for manipulation when using proxies. How can we ensure the integrity of proxy voting systems or other situations where proxies are used?
Imagine you are a researcher studying animal intelligence. What are some alternative proxies you could use besides tool use or puzzle-solving abilities?
Do you think brain scans are a reliable proxy for consciousness? Why or why not? What are the challenges of studying consciousness scientifically?
The discussion of the Hemline Index and lipstick sales as proxies for economic trends raises the question: Can economic downturns influence seemingly unrelated aspects of society? Discuss potential explanations for these correlations.
The example of ice cream sales and shark attacks highlights the importance of considering alternative explanations when using proxies. Can you think of other examples where seemingly correlated phenomena might not have a causal relationship?
Are there any situations where you think a weak correlation between a proxy and a target variable might still be useful? Explain your reasoning.
The passage mentions the importance of understanding the mechanism linking a proxy to the target variable. How can researchers improve our understanding of these mechanisms?
Should policymakers rely on proxies like standardized tests to make decisions about education or employment? Why or why not? What are the potential consequences of doing so?
How can we balance the need for accurate measurement in scientific research with the limitations of directly observing some phenomena?
Do you think the use of proxies will become more or less important in scientific research in the future? Why? What are some potential advancements in technology that could influence the use of proxies?
The concept of proxies can be applied to many aspects of life beyond scientific research. Think of a situation in your own life where you might use a proxy to judge something. Discuss the limitations and potential benefits of using a proxy in this scenario.

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