The graphic above plots the ISI against the V-Dem Liberal Democracy Index, a standard measure of liberal democracy developed by political scientists at the Varieties of Democracy research centre. Each country is given a score ranging from 0 (highly autocratic) to 1 (highly democratic). Clear patterns are visible. While some autocratic regimes (such as China) may provide significantly for the wellbeing of future generations, the majority of autocratic regimes do not. In addition, almost all highly democratic regimes and most democracies in general give more to future generations.

State fragility is indexed annually by the Fund for Peace, with a score of 0 representing highly stable states and 100 denoting highly fragile states. A clear relationship with intergenerational solidarity emerges, albeit inverted; more stable states are more likely to sacrifice in the interests of future generations. Although a causal relationship between stability and solidarity seems plausible, it may be that intergenerational solidarity itself has a stabilising effect on states, or that other factors (such as wealth) may influence both of these.

Decentralisation also appears to be related to intergenerational solidarity in much the same way as democratisation and stability. One point worthy of particular attention is the pattern in more autocratic countries that score highly in the ISI, such as China and Vietnam - these countries are markedly more decentralised than other autocracies such as Egypt and Saudi Arabia.

Political decentralisation is here assessed using an index proposed in a working paper for the World Bank in 2012, corrected for population, area and homogeneity and log adjusted; low scores indicate a centralised structure of governance, and vice versa for high scores.

The index not only allows for quantitative research into the relationship between intergenerational solidarity and political variables as indicated above; it could also be applied to exploring the cross-cultural roots of intergenerational solidarity in fields such as economics and social psychology.

This work is just beginning, yet is necessary if we are to understand ourselves well enough to make the sacrifices necessary to solve intergenerational problems such as climate change and the cycle of poverty.

For more information on the precise features of the index and where its data come from, see the method page. The data are also available for those who want to do their own analysis.