What proxies to use for flow-through effects?

Summary: When assessing altruistic interventions from a long-run perspective, particularly ones which do not act directly on the long-run (like averting human extinction) assessing flow-through effects is essential. In this post I raise some possible metrics to use in assessing flow-through effects. The causal relationships between them are unclear, and exogenous interventions to boost a metric may break correlations with other outcomes: they are intended as a set of candidates to reference in later discussion. Additional candidates are welcome in the comments.


Total GDP
Overall economic output is a proxy (an imperfect one) for the total productive capacities of humanity. As total GDP increases, the share of income required to pay for fixed cost interventions such as asteroid defense or geoengineering falls. On the other hand, fixed cost harms also become more likely. Increased GDP also pushes forward technological advance, although probably less so than total capacities (other factors influence technological change as well).

Total population
We might distinguish population from GDP for several reasons. Some fields may be especially labor-intensive, suffering from Baumol's cost disease, and scaling better with population than GDP. A larger population may increase the absolute supply of 'genius.' Even if additional people are not currently contributing much to GDP, they increase the potential for gains from development or migration.

GDP/GNI per capita/total of log income
One of the most striking features of the last few centuries is that individual incomes in much of the world have climbed far above subsistence levels. In international analyses we might use GDP per capita to summarize this, but adding up the log incomes of individuals may give a more elegant and relevant measure.

In the world today there are very strong correlations between national GDP per capita and many other plausible measures of flow-through effects. For example, the Human Development Index combines income per capita with life expectancy and educational attainment, but since the latter two inputs are highly correlated with income per capita, national HDI remains very similar to national per capita income alone (here's a nice plot from Gapminder), and probably even more similar to national total log income.

High per capita wealth is correlated with significant differences in the World Values Survey, as Robin Hanson discusses in this post.

Educational inputs (years of schooling, distribution of schooling)
Measures here would include total and average years of schooling completed, frequency of tertiary education graduates, and similar. In addition to effects on other measures discussed here, increased education is a plausible candidate for increased "wisdom" on the part of the general population and key decisionmakers.

Educational outputs and quality, test scores
In a conversation with GiveWell, Lant Pritchett of the Center for Global Development says that measures of educational inputs (school constructions, years of school) fall substantially short, and that actual student learning should be a larger focus. The research of economist Eric Hanushek of Stanford, among others, makes the case that student test scores are powerfully correlated with long-run outcomes for individuals (later income, education, crime) and even moreso for economic growth at the national level. And again, this is a promising measure of wisdom.

Life expectancy/healthy life expectancy/biometrics
Life expectancy is an important measure of the welfare of individuals, and healthy life expectancy, adjusted for morbidity is even better. However, it is less clear how this measure relates to long-run impacts.

Something like "working life expectancy" might better capture potential impacts on total capacities (perhaps supplemented by more accurate measures of the productivity effects of aging). Older populations have been observed to be less violent, both individually and at the national level (although the later has many confounds). Older individuals have views that are more characteristic of earlier periods (relative to the young), which could be bad if one believes there is ongoing moral progress from generation to generation.

Other biometric measures of health can capture improved human biological capacities, e.g. the literature using human height to track improvements in nutrition, disease prevalence, and standard of living.

International peace and cooperation
War is a major potential source of global catastrophic and even existential risk. While several of the above measures (such as per capita income) have negative correlations with conflict and violence, other measures are available. These could include:

• The number of nuclear weapons
• The number of nuclear-armed states
• Per capita death rates from violence
• Rate of wars and civil wars
• The frequency of military high alerts, confrontations, and interventions
• Extent of economic ties between states
• Scores on democracy indexes, based on Democratic Peace Theory
• The quantity and distribution of military spending, the number of states with no armies
• High-quality forecasts (e.g. using prediction markets, "super-forecasters" and other enhanced forecasting methods) to track changes in the potential for lower-frequency high-impact conflict
• Homicide rates and disorganized violence

Institutional quality metrics

Measures of institutional quality face confounding with other positive characteristics, and their definitions may be politically biased, but they both have predictive power and plausibility. Better ones are surely possible, but some noteworthy existing ones include:

• Corruption perceptions
• Press freedom
• Democracy
• Ease of Doing Business

Measures of cost-effectiveness in government spending, the accuracy of scientific claims on which policy is based, and government forecasting accuracy could be helpful additions.

Environmental quality

Many environmental impacts will appear in healthy life expectancy, GDP, test scores (e.g. lead and mercury poisoning) and similar measures. However, long-term and lagged effects need to be accounted for as well, e.g. the accumulated burden of greenhouse gas emissions with long lifetimes.

Technological improvement

One fairly broad (although imperfect) measure of technological improvement is total factor productivity (TFP), a measure of efficiency of production in terms of labor, capital, materials, and other inputs. Labor productivity is also useful, and individual technologies have many relevant metrics:

• Computations per dollar
• Agricultural yields
• Solar panel cost per kilowatt-hour
• Telecommunications bandwidth
• Natural language translation word error rates

General technological advance increases human capacities and wealth, but accelerates progress towards potentially dangerous technological transitions (affecting the characteristics of society at the time, so long as there are other ongoing changes in society), with the net effect ambiguous. Progress in particular technologies may be better or worse. 

Scientific output and quality

There is a field of scientometrics, but it is focused on inputs, such as the number of scientists, R&D spending, papers published, patents issued, and citations. There is no analog to student test scores to clearly assess quality, although there have been some efforts to trace commercial production to scientific effort (e.g. in pharmaceuticals, where the connections are comparatively clear). Recent efforts to improve scientific methodology suggest measures such as the reproducibility of scientific findings, but these do not track the utility of the findings. Nonetheless, better measures could be very helpful indeed in this area.

And more
Again, I invite new candidate proxies for flow-through effects in the comments.