Yale University’s William Nordhaus divided the world into cells, by lines of latitude and longitude, and plotted each one’s climate, output, and population. He concluded that the hotter the average temperature, the less productive people could be.18 According to Geoffrey Heal of Columbia University and Jisung Park of Harvard, a hotter-than-average year is bad for productivity in hot countries, but good in cold ones: crunching the numbers, they conclude that human productivity peaks when the temperature is between 65 and 72 degrees Fahrenheit.19
