increase, there is no rule here,it might do that for 3 days and then not work,and then may switch over to where they both go up and down together, so watch it, if it works that day use it, but be prepared for a switch
the SP500 is a weighted index, RENTEC sends in huge volume of trades in 'stocks'... a program buy or sell order in a select few weighted stocks controls the index.
Just saw this...when you say "a select few weighted stocks controls the index" do you mean the top 15 to 20 stocks based on market cap --- e.g., xom, ge, msft, and so on?