another possibly dumb question

[Leslilake1 at aol.com]

I was looking at the graph of the dow jones on Yahoo that goes back to the 
20's, which I do every so often.  But I'd never noticed that there were two 
settings, logarithmic and linear.  The log chart, the one I normally look at, 
makes the rise in value since the twenties look negular and gradual 
(linear?).  But the linear chart gives a different picture - looks gradual 
and regular (linear?) until about 1985, when suddenly there's this 
exponential spike (from 2000 to 11000 points in about 15 years).  It reminded 
me of population models (snowshoe hares and foxes, fish harvests, etc.) from 
an ecology class I took years ago - slow growth, then exponential growth, 
then die-off.   Is there any significance to this?  Or, alternatively, do 
most things that "grow" in units (like populations, or money) tend to follow 
this same pattern?     

Les