Below is the data of Dow Jones Industrial Average declines in the period indicated as a recession according to the National Bureau of Economic Research (NBER) from 1902 to 2009. The percentage change is arrived at by taking the first trading day of the month indicated as the beginning of a recession and the last trading day of the month indicated as the end of the recession.
| recession begins | recession ends | Dow % change |
| September 1902(IV) | August 1904 (III) | -18.00% |
| May 1907(II) | June 1908 (II) | -13.45% |
| January 1910(I) | January 1912 (IV) | -17.36% |
| January 1913(I) | December 1914 (IV) | -38.27% |
| August 1918(III) | March 1919 (I) | 6.03% |
| January 1920(I) | July 1921 (III) | -37.38% |
| May 1923(II) | July 1924 (III) | 4.87% |
| October 1926(III) | November 1927 (IV) | 24.12% |
| August 1929(III) | March 1933 (I) | -84.20% |
| May 1937(II) | June 1938 (II) | -23.32% |
| February 1945(I) | October 1945 (IV) | 21.33% |
| November 1948(IV) | October 1949 (IV) | 0.94% |
| July 1953(II) | May 1954 (II) | 21.57% |
| August 1957(III) | April 1958 (II) | -9.95% |
| April 1960(II) | February 1961 (I) | 7.48% |
| December 1969(IV) | November 1970 (IV) | -1.36% |
| November 1973(IV) | March 1975 (I) | -19.04% |
| January 1980(I) | July 1980 (III) | 5.78% |
| July 1981(III) | November 1982 (IV) | 3.93% |
| July 1990(III) | March 1991(I) | 0.49% |
| March 2001(I) | November 2001 (IV) | -5.73% |
| December 2007 (IV) | June 2009 (II) | -26.59% |
| Average DJIA % change | -9.00% |
This data indicates that in periods of recession, the Dow Jones Industrial Average has had an average loss of –9% from the beginning to the end of a recession, as indicated by the NBER. Slightly less than half (45%) of the indicated periods saw the Dow Jones Industrial Average net a positive gain in the index (excluding dividends). The average length of a recession since 1902 has been 14.5 months while the recovery phase has lasted approximately 44.5 months.
Already this current bull market has run 103 months. For this reason, it is necessary to expect that a recession is coming. However, if the above data is any indication, then there should be little reason to fear the impact on the stock market if given the appropriate time horizon. The data suggests that if you don’t have a minimum of 5-year time horizon for your investments then some money should be either set aside or the principal of existing holdings should be sold.