The unemployment rate for the years 1923-29 was 3.3 percent. In 1931 it jumped to 15.9, in 1933 it was 24.9 percent.
According to the Census, unemployment had dropped under 10% by 1941, and appears to have decreased to approximately 7% by the end of 1941. If unemployment were calculated the same way then as now that actual unemployment during the Depression would have been significantly lower, especially once the New Deal came in. Apparently the official figures counted as unemployed those working on government projects (WPA, CCC, etc), a standard not used today.