Many mistakenly look to the stock market as the leading indication of economic security. The true culprit is the DEBT market, not the stock market, that leads to depressions and recessions. A recession, in comparison to a depression, is merely a minor impact that could be isolated to one nation. Unemployment will typically rise up to 10% in a recession, whereas a depression could see a 25%+ turn in unemployment. A lack of work leads to civil unrest and upheaval. Depressions are never isolated to one nation as they spread as a contagion throughout the world.
You could take the stock market down 30%, even 40%, and still not create a depression. Yet, if you undermine government debt by far less, you will create a severe economic downturn. Look to the banks. Under law, banks are required to use government debt as a reserve. Undermining government debt simply wipes out the banking industry as we have historically seen when bank after bank is forced to shutter.
During the Great Depression, sovereign defaults began in Europe. Look at what happened in 1931 when Europe defaulted on its debt, as did Asia and so forth since depressions become contagions. This pushed the dollar higher but not the US share market. Note that the dollar rose in value during World War I, the 1931 Sovereign Debt Crisis, and again for World War II. During those waves of capital flows, the bulk of that capital always moved into government bonds.
This is an oversimplified version of this message but you can read more on the 1931 Sovereign Debt Crisis throughout this website. Governments default and then that often leads to a regime change. The incoming regime will simply say, “Oh, that was the debt of the last government and we need not pay.” Listen, the stock market could plunge 20% and the banks would be OK. But if you saw the same in the debt market, in particular sovereign debt, you’re in serious trouble.