Until the Wall Street Crash of 1929, the economy had been measured in tonnes of grain and steel, and because of the crash- economists and politicians decided they wanted some grip over the scale of output of the economy- so they turned to a brilliant young scientist called Simon Kuznets and asked him how they should be measuring economic output. His answer was published in 1930s- he figured out a way to add-up all the tonnes of grains and steel and create a national income figure. He gave the caveat that it would scarcely be taken as the measure of welfare of a nation because it didn’t include all the value created in a community, all the unpaid caring work at home, and only measured what was sold- not what was used-up!