Final answer:
Farmers' earnings in the 1920s declined dramatically due to overproduction and plummeting agricultural prices post-World War I, leading to an inability to repay debts and causing foreclosures and a rural-to-urban shift.
Step-by-step explanation:
The earnings of farmers during the 1920s saw a significant decline. After World War I, agricultural prices plummeted due to overproduction, with fewer buyers in the post-war period. Farmers had expanded during the war to meet the demand, often borrowing money for land and equipment. However, when prices dropped, they struggled to repay loans, which led to widespread bank foreclosures on their property and a movement of people from rural areas to urban centers. Congress attempted to introduce federal price supports, but these measures were vetoed by President Coolidge, leading to further strife in the agricultural sector. As the 1920s ended, the lowered demand and overproduction caused further economic imbalance which contributed to the onset of the Great Depression in the 1930s.