"Based on what I think I have a feel for, I would observe that every decade had its own unique characteristics...
1920s = "roaring" - slow growth early building to a boom later, low inflation, extreme inventiveness, stock market boom.
1930s = "depression" - basically the opposite of the 1920's, bad for stocks and good for government bonds.
1940s = "war/post war" - the economy and markets were classically war dominated.
1950s = "stability" - good stock and bond markets.
1960s = "economic acceleration" - greater optimism and prosperity; good for stocks.
1970s = "stagflation" - good for inflation hedge assets and bad for stocks and bonds.
1980s = "disinflation" - bad for inflation hedge assets and good for stocks and bonds.
1990s = "roaring" - slow growth early leading to a boom later, low inflation, extreme inventiveness, stock market boom.
...yet, at the ends of each of each of these periods, most people assigned a high likelihood to the future being similar. In other words, though the environments have always changed dramatically (in fact, each decade was more likely to be opposite than similar to the decade that preceded it), most people who experienced consistent reinforcement for 10 years were inclined to believe that this would continue indefinitely."