During what time periods did the size of investment banks change?

a. In the 1920s, as US consumer spending increased, investment banks grew in size to provide credit to American consumers.

b. Shortly after World War II, the size of investment banks grew thanks to the postwar economic boom. 

c. During the inflationary times of the 1970s, investment banks grew as investors sought investments that kept pace with inflation.

d. Deregulation in the 1980s and changes in corporate structures in the 1990s resulted in growth in the size of investment banks.