Answer:
all Americans
Explanation:
During the late 1920s, the stock market in the United States boomed. Millions of Americans began to purchase stock, causing the market to dramatically increase in value. Unfortunately for the economy, so many Americans invested money in the stock market that stocks became inflated in price.
This is called monogamy as opposite to polygamy (multiple spouses at the same time).
This is of course a very complex question that does not have a definitive answer, but 1850s would be a good decade to start counting as "Modern". This was a decade of the telegraph and Darwin's The Origin of Species.
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