basically stock market crash is the consequence of an unstable economy, not the cause of it. The primary cause for the erractic behaviour of western economies during the 20th century was due mainly to the existence of central banks. Central banks were introduced under the belief that you could eliminate economic cycles forever by controlling the money supply; history has shown that certainly wasn't the case. To stimulate an economy, a central bank will keep the discount lending rate low.

However, as the money under a central banking system is usually fiat the expansion of the money supply devalues the purchasing power of the money already in the system, also known as inflation. This is the reason why we are seeing the first of a series of market corrections that will inevitably lead to a major crash - years of money expansion in a desperate attempt to ensure that recessions are brief.

I read an article quite a while ago that listed about 40 different factors, a Chinese economic recession being one of them, that any one of those factors by themself could lead the economy into a recession and that the possibility of any of those factors not occuring is unlikely. The only way you can ensure that an economy remains relatively stable is to eliminate central banks and return to a commodity based money supply.