WASHINGTON —Hotter days mean less cold cash for Americans, according to a new study matching 40 years of temperatures to economics.

Days that averaged about 77 degrees ended up reducing people’s income by about $5 a day when compared with days that were about 20 degrees cooler. A county’s average economic productivity decreases by nearly 1 percent for every degree Fahrenheit that the average daily temperature is above 59, says a National Bureau of Economic Research working paper released Monday.

And, the study’s authors predict, if the world continues on its current path of greenhouse gas emissions, even warmer temperatures later this century will squeeze the U.S. economy by tens of billions of dollars each year.

This is not from storms, drought or other weather disasters – just the sweat of daily heat.

The paper by a pair of economists at the University of Illinois and University of California, Berkeley, has not yet been peer-reviewed but is part of work done for the nonpartisan economics research center that is widely cited for determining when the country is in and out of recessions. In comments from other researchers, the new study was criticized for its methods and conclusions by some economists and policy experts but praised by others as groundbreaking.

The study tries to find common ground between the hard physical science of meteorology and the softer science of economics. In doing so, the researchers used new complex statistical techniques crunching more than 76,000 data points.