Answer based on context:

The stock market crashed in October 1929, and ushered in the Great Depression. By the winter of 1932-33, the economy was so perilous that the unemployment rate hit the 25 percent mark. Unions lost members during this time because laborers could not afford to pay their dues and furthermore, numerous strikes against wage cuts left the unions impoverished: "one might have expected a reincarnation of organizations seeking to overthrow the capitalistic system that was now performing so poorly. Some workers did indeed turn to such radical movements as the Communist Party, but, in general, the nation seemed to have been shocked into inaction". Though unions were not acting yet, cities across the nation witnessed local and spontaneous marches by frustrated relief applicants. In March 1930, hundreds of thousands of unemployed workers marched through New York City, Detroit, Washington, San Francisco and other cities in a mass protest organized by the Communist Party's Unemployed Councils. In 1931, more than 400 relief protests erupted in Chicago and that number grew to 550 in 1932. The leadership behind these organizations often came from radical groups like Communist and Socialist parties, who wanted to organize "unfocused neighborhood militancy into organized popular defense organizations".

How many more relief protests erupted in Chicago between the number recorded in 1931 and the number in 1932?
150