Table 22.1 labor union membership year number of members 1933 2,857,000 1934 3,728,000 1935 3,753,000 1936 4,107,000 1937 5,780,000 1938 8,265,000 1939 8,980,000 1940 8,944,000 1941 10,489,000 1942 10,762,000 1943 13,642,000 1944 14,621,000 1945 14,796,000 which event had the most impact on union growth according to the information shown in the chart and your knowledge of history?