Taxation.

This is coolbert:

That United States subsequent to the end of the Second World War [WW2] a radically different society as what existed in 1939.

General societal prosperity of a nature hitherto unimaginable as to scale one result.

Automobile ownership for adult males in the U.S. before the war about 25 %.

By 1947 nearly 100 % of adult American males able to afford and own an automobile.

So in the aftermath of the Depression Era and the end of the war some VERY PROFOUND CHANGES OCCURRING IN U.S. SOCIETY!

This too. The personal income tax.

To pay for the war, increased taxation as might well be expected. NOT however, merely a war-time temporary measure, but something that became permanent.

From "The Guns at Last Light" by Atkinson:

"The entire war had cost U.S. taxpayers $296 billion dollars, roughly $4 trillion in 2012 dollars"

"To help underwrite a military budget that increased 8,000 percent, Roosevelt had expanded the number of those taxpayers from 4 million to 42 million."

That  percentage of working American adults paying income tax about 10 % in 1939 dramatically expanded during the war to include nearly 100 % of working adults by 1945 paying some sort of income tax.

Again, not just persons paying taxes, but paying personal income tax. That was a rarity in 1939, but not so from 1945 onward. And continues unabated even to this very day, as we are all aware.

coolbert.