The trend was different 100 years ago. The norm in those days was for sporadic and often quite painful bear markets. A quick-running downturn in 1920 knocked prices by more than 40 per cent. Another one, from 1928-32, produced a total decline of 60 per cent.

A major trend change occurred in the second-half of the century. Since1950, there were 14 separate downturns. In other words, one began every four years or so, on average.

Those who began to invest in the rip-roaring 1980s or 1990s are especially likely to be surprised by these figures. Unfortunately, that powerful two-decade long advance probably was probably a once-in-a-century experience.

We seem to have gotten back on track in recent years with separate downturns in 1998, 2000-3 and 2007-8.

History makes a clear point. The road to long-term capital accumulation must either include working and saving or being born into the right family. Stock market gains of the magnitude seen at the end of the last century probably will no longer do the trick.

Another trend change worth noting is the role of financial institutions in triggering bear markets.

Go back to the 1950s, '60s and '70s and you will find that interest rate changes and bank lending restrictions played a role in many bear markets.

But these changes and restrictions were typically forced upon financial institutions by the government of the day. These institutions were frequently buffeted by government policies or broad economic forces, just like the rest of us. They were often victims as well as victimisers.

The world changed in recent years - big time. Indiscriminate lending practices and high leverage provided by leading financial institutions were implicated in each of the last three downturns.

Recall that the collapse of the Long Term Capital Management hedge fund triggered the 1998 downturn. LTCM went belly up after bank loans allowed it to leverage some of its bets by a factor of 100:1.

Speculative lending to investors in start-up tech companies in the late-1990s contributed to the Tech bubble and the bear market of 2000-3

The bear market of 2007-8 was triggered by sub-prime real estate loans, coupled with clever ways of repackaging these loans in a highly leveraged fashion.

To be fair, low interest rates by the Greenspan-led Federal Reserve also contributed to the problem. Even so, there is an old expression that war is too important to leave to the generals. Perhaps the same thought should now be applied to the link between the economy and financial institutions.

We now know that short-term greed and mismanagement by top financial executives can slam the entire economy, not just one errant company. There is an urgent need for more supervision and regulation. Otherwise, we must prepare for future banking-caused stock market drops.