Income classification based on the World Bank (2012) income classification. This has tended to be the case in the majority of OECD countries, although the degree of protection and other forms of trade-distorting support has declined significantly over the past 25 years (Box 3.1). However, comparative advantages in food production are not irreversibly fixed. While heavily influenced by initial endowments of land, water, climate, topography, soils and the prevalence of pests and diseases, whether a country is a net food exporter or importer also depends on its past investments in agriculture-related physical and human capital, in institution-building and in technology improvement.