Table 2.
Description of regional variables.
| variable | measure | source | rationale |
|---|---|---|---|
| % paddy rice field | paddy fields area/total cultivated area | China Statistical Yearbook, 2002 | paddy rice required more work and coordination to build and operate irrigation systems |
| GDP | GDP per capita in 2012 | China Statistical Yearbook, 2013 | this measures regional economic development |
| % cultivated land | hectares of cultivated land/total province land | China Statistical Yearbook, 1996 | this measures the density of farming in general |
| environmental rice suitability | environmental suitability for high-input rainfed rice | UN Global Agro-Ecological Zones Database | environmental rice suitability (regardless of whether people actually farm rice there) is an instrumental variable to test reverse causality—the possibility that areas that were collectivistic to begin with chose to farm rice [8] |
| contact with herding cultures | people from traditionally herding ethnicities/total population | China Population Statistical Yearbook, 2002 | research has found that herding cultures tend to be more individualistic than nearby farming cultures [34] |
| distance to coast | The distance of provincial capital to nearest coast (100 km). Coast province = 0. | Marine Regions Database | Distance from the coast can be a proxy for modern and historical development. Coastal provinces also had more access to sea transport and potentially more diverse ideas and cultures. |
| average temperature | average high, low temperatures in January and July | Zuzu Che Weather Records | some researchers have argued that hotter areas are more collectivistic, and the temperature is also correlated with disease prevalence [36] |
| latitude | average of northernmost and southernmost province latitude | Google Maps | In China, rice is highly correlated with latitude. Latitude is a proxy for other environmental factors such as temperature and disease. Testing latitude checks the robustness of rice against latitude. |
| longitude | average of easternmost and westernmost province longitude | Google Maps | testing longitude checks the robustness of rice against longitude |
| historical pathogen epidemics | rates of epidemic diseases in the Ming and Qing Dynasty (1368–1911) | [38] | pathogen prevalence theory argues that environments with higher rates of communicable disease tend to be more collectivistic [39] |
| history of rebellion | an index of the frequency of mass rebellions during the Qing Dynasty | [40] | rebellion may have affected genetic selection or it may reflect regional cultural differences |