Fig. 3: Relationship between GDP and number of agri-environmental policies.

a, Each dot represents a country in the database. The fitted line and corresponding 95% confidence interval to indicate the general trend come from a linear regression. Countries with a higher GDP implement more agri-environmental policies than those with a lower GDP (N = 186). b, As in Fig. 1, we can use an augmented policy effort measure (‘policy intensity index’) that weights the simple number of policies by the average policy stringency and enforcement of countries as well their level of corruption. The empirical relationship between this measure and the GDP of countries is even stronger than the relationship with the simpler measure shown in a. Whereas the relationship with the simpler measure is approximately linear, the relationship with the augmented measure is approximately exponential. The fitted line and corresponding 95% confidence interval to indicate the general trend come from a nonlinear regression (N = 176). As shown in Supplementary Fig. 5, a similar but reversed pattern appears if one replaces the GDP of countries with the agricultural share of their GDP.