The long-term, more than 100-year performance: Since 1900 (end-of-year 1899), through 2012, I estimate the average total return/year of the DJIA (Dow Jones Industrial Average) was approximately 9.4% – 4.8% in price appreciation, plus approx 4.6% in dividends. (Some numbers may not add up due to rounding.)

Since 1929 (year-end 1928 — i.e., before the crash), through 2012, the return was 8.8% (4.6%, plus 4.2%) [note: see The 1929 Stock Market Crash]

Since end-of-year 1932 (i.e., after the crash): 11.1% (7.0%, plus 4.2%)
The average annual stock market return for the past twenty-five calendar years (since 1987) was 10.6% (7.9%, plus 2.7%) The market was up over 40% before the October 19, “Black Monday," crash. After a significant recovery, the Dow actually closed up 6% for the year.

Stock market returns for the last 20 years (since 1992): 9.6% (7.1%, plus 2.4%) In the middle of one of the longest bull markets in history. [see below for additional 20-year periods]