Based on the data provided, a bull market is typically identified by rising stock prices. In the years provided:
- In 1927, the Dow Jones was 150.
- In 1928, it rose to 200.
- In 1929, it rose further to 320 before peaking at 380.
- However, from 1930 onward, the Dow Jones shows a decline (290 in 1930, 190 in 1931, 80 in 1932, and 50 in 1933).
The only year with a continued increase before experiencing a peak is 1928. Therefore, the bull market year is:
1928.