then the stock market crash known as Black Tuesday on October 29, 1929, and lasted through much of the 1930s. The entire decade is marked by widespread unemployment and poverty, although deflation (i.e. falling prices) was limited to 1930–32 and 1938–39. Prices fell 7.02% in 1930, 10.06% in 1931, 9.79% in 1932, 1.41% in 1938 and 0.71% in 1939. Economic interventionist policies increase in popularity as a result of the Great Depression in both authoritarian and democratic countries. In the Western world, Keynesianism replaces classical economic theory. In an effort to reduce unemployment, the United States government created work projects such as the Civilian Conservation Corps (CCC) which was a public work relief program that operated from 1933 to 1942 to maintain National Parks and build roads. Other major U.S. government work projects included Hoover Dam which was constructed between 1931 and 1936. Rapid industrialization takes place in the Soviet Union. Prohibition in the United States ended in 1933. On December 5, 1933, the ratification of the Twenty-first Amendment repealed the Eighteenth Amendment to the United States Constitution. Drought conditions in Oklahoma and Texas caused the Dust Bowl which forced tens of thousands of families to abandon their farms and seek employment elsewhere. Science and technology Technology Many technological advances occurred in the 1930s, including: On March 8, 1930, the first frozen foods of Clarence Birdseye were sold in Springfield, Massachusetts, United States. Nestlé releases the first white chocolate candy as the Milkybar.; Ub Iwerks produced the first Color Sound Cartoon in 1930, a Flip the Frog cartoon entitled "Fiddlesticks"; In 1930, Warner Brothers released the first All-Talking All-Color wide-screen movie, Song of the Flame; in 1930 alone, Warner Brothers released ten All-Color All-Talking feature movies in Technicolor and scores of shorts and features with color sequences; Air mail service across the Atlantic Ocean began; Radar was invented, known as RDF (Radio Direction Finding), such as in British Patent GB593017 by Robert Watson-Watt in 1938; In 1933, the 3M company marketed Scotch Tape; In 1931, RCA Victor introduced the first long-playing phonograph record. In 1935, the British London and North Eastern Railway introduced the A4 Pacific, designed by Nigel Gresley. Just three years later, one of these, No. 4468 Mallard, would become the fastest steam locomotive in the world. In 1935, Kodachrome is invented, being the first color film made by Eastman Kodak. In 1936, The first regular high-definition (then