You might have to define your particular definition of the average American. Some will paint this question as a one percenter, class struggle argument and some will go by the statistically average American.
Using the definitions of the average American of 1929 and the extended aftermath of the Depression would answer the question differently than the average market holdings of the statistically average American of 2008.
In 1929 ( and an extended period after ), the statistically average American was more helped by being able to keep his job than the stock market, whereas the downturn of 2008 was likely to effect the market holdings of these individuals in a different way if ( while staying fully invested ) they basically regained their losses in two years. In either case, you can't help but feel that time in the market, amounts in the market, and rolling 5 year periods will give you different results. The majority of which will have the "average" American benefiting handsomely from stock market gains.
That might be too clinical a way of looking at it in reference to the question, but the fact remains that it can depend. A 60 year old man just above the poverty line still investing 4% of his salary every month since age 25 vs. someone who inherited 400K in mutual funds in 2007 ( with no other investments ) and lost 60% of it in 2008 and left the market...two years before retirement .
Not having 3-4% interest rates could potentially push the average retired couple into riskier investments than their profile warrants and bad timing will generate something from which it could take much longer to recover. My dad retired at the end of 1986, was invested conservatively, and it still took him almost 5 years to recover from Oct. '87. Below average and above average ( statistical persons, amounts and intelligence ) will yield different results over time.
