We’ve seen some scary numbers lately, especially on unemployment. Even with the recent rebound for retail sales, the picture remains the worst since modern federal records began in 1948.

Or since the Great Depression.

Last month Federal Reserve Gov. Lael Brainard explained our situation this way: “Last year, national unemployment had fallen to its lowest point in over five decades. Today, unemployment has surged to levels not seen since the Great Depression.”

All this makes it important to examine an event whose origins and cures remain debated. What’s not debated: It was the worst economic collapse of modern times, with world-shaking consequences.

The Depression is often seen beginning with the stock market crash of October 1929. The biggest reasons: overvalued stocks, speculator fraud and over-reliance on purchasing shares on margin (buying on credit, which depends on prices going up).

Yet trouble was gathering before the crash.

The banking system was rickety. Some 8,000 banks were members of the Federal Reserve System, but twice that many were not. Even some of their reserves were fictitious.

Some scholars claim the economy was recovering from the stock collapse when bank panics took it down. Between 1929 and 1933, 7,000 banks failed.

Faced with these problems in 1930, the Federal Reserve made a disastrous blunder, tightening the money supply and failing to act as lender of last resort to key banks.

Economists Milton Friedman and Anna Schwartz made this case so convincingly that future Fed Chairman Ben Bernanke in 2002 apologized for the central bank’s failure. The occasion was Friedman’s 90^th birthday and Bernanke said, “Regarding the Great Depression. You’re right, we did it. We’re very sorry. But thanks to you, we won’t do it again.”

The Fed — and much of the developed world — was constrained by the gold standard, which connected money to the precious metal.

Yet another lever down the mountainside was the Smoot-Hawley Tariff of 1930. Intended to protect American jobs, the act backfired spectacularly.

All told, a severe contraction was driven to become the Great Depression. From 1929 to 1933, gross national product fell by one third, the stock market lost 80% of its value and unemployment hit 25%. Severe deflation set in.

In his memoirs, Hoover quoted Treasury Secretary Andrew Mellon, chief architect of the laissez-faire 1920s policies, as saying, “Liquidate labor, liquidate stocks, liquidate the farmers, liquidate real estate. Purge the rottenness out of the system.”

Hoover didn’t agree. A Theodore Roosevelt Progressive, Hoover made his reputation coordinating aid to millions during and after World War I. At the punitive Versailles talks that forced Germany to accept sole blame for the conflict, John Maynard Keynes said Hoover was the only participant who “emerged from the ordeal of Paris with an enhanced reputation.”