A question for you economic historians.
I'm a bit curious as to how the New York Stock Exchange and the London Stock Exchange managed to remain open during the Second World War. Investors today count on a steady stream of cash flows or growth via securities analysis to build their portfolios. Since a great deal of trade was interrupted by the outbreak of the War and an even greater number of corporations were effectively or outrightly nationalized into war service under strict legislation to prevent war profiteering, how could the Exchange be open for business? Presumably no one was trading stock on speculation/arbitrage during this time, but long-term value holding must have also been a relatively new concept in 1939 even when one takes into account the fact that most Americans didn't invest for retirement in securities.
Lots of people were still trading. The NYSE has historical records that show this. 1945, for instance, was significantly busier than 1940.
Trade volume is also a really, really good indicator of how the average, well-informed citizen felt about the war. After Pearl Harbor and the string of Japanese victories in East Asia, trading was even lower than it had been during the Great Depression (in the above link, April of 1942 sees daily trades drop to 130,000 -- if you look at the figures from the previous decade, the lowest for 1932 seems to be around 300,000). By the beginning of 1943, however, we start to see strings of million-plus trade days. That's about six months after the US wins a decisive victory at Midway and shortly after Tokyo orders its troops to pull out of Guadalcanal; it's also not terribly long after the Soviets announce that they've completed the encirclement of Paulus at Stalingrad. The turning point of the war is reached and the trades reflect that.
You can't have capitalism without capital. And the NYSE is where lots of that capital changes hands.