51 countries as “resource-rich”, defined as countries which derive at least 20% of exports or 20% of fiscal revenue from nonrenewable natural resources. 29 of these countries are low- and lower-middle-income. Common characteristics of these 29 countries include (i) extreme dependence on resource wealth for fiscal revenues, export sales, or both; (ii) low saving rates; (iii) poor growth performance; and (iv) highly volatile resource revenues. A 2016 meta-study found weak support for the thesis that resource richness adversely affects long-term economic growth. The authors noted that "approximately 40% of empirical papers finding a negative effect, 40% finding no effect, and 20% finding a positive effect" but "overall support for the resource curse hypothesis is weak when potential publication bias and method heterogeneity are taken into account." A 2018 study showed that most specifications, the impact of oil correlated with regime leaders as well as being between two and three times larger than the marginal effect of increases during the leader's term. A 2021 meta-analysis of 46 natural experiments found that price increases in oil and lootable minerals increased the likelihood of conflict. A 2011 study in the journal Comparative Political Studies found that "natural resource wealth can be either a “curse” or a “blessing” and that the distinction is conditioned by domestic and international factors, both amenable to change through public policy, namely, human capital formation and economic openness." Dutch disease Dutch disease, defined as the relationship between the increase in the economic development of a specific sector (for example natural resources) and a decline in other sectors, first became apparent after the Dutch discovered a huge natural gas field in Groningen in 1959. The Netherlands sought to tap this resource in an attempt to export the gas for profit. However, when the gas began to flow out of the country, its ability to compete against other countries' exports declined. With the Netherlands' focus primarily on the new gas exports, the Dutch currency began to appreciate, which harmed the country's ability to export other products. With the growing gas market and the shrinking export economy, the Netherlands began to experience a recession. This process has been witnessed in multiple countries around the world including but not limited to Venezuela (oil), Angola (diamonds, oil), the Democratic Republic of the Congo (diamonds), and various other nations. All of these countries are considered "resource-cursed". Dutch disease makes tradable goods less competitive in world