This becomes particularly clear when we compare employment trends in different economic sectors. (educationnext.org)
As you can see, even in a 19 - stock portfolio, I am able to have a pretty good degree of diversification across different economic sectors. (dailytradealert.com)
The time scales of stock turnover vary enormously between different economic sectors, but appear to be very long for most greenhouse - gas emitting sectors. (ipcc.ch)