When conducting back tests on searches that use historical watchlists like W-O-W, S&P 500, NASDAQ 100, the back test pulls from the current date watchlist rather than the stocks that show up in the search from the historical date.

The right stocks show up if you go back to a historical date (eg 1/5/2010) and view the watchlist with the Viewers Tab or run a unisearch on that historical date. But then when you run the back test, you can see when looking in the trade history or transaction summary, the back test not pulling stocks that should have been selected on the historical date. Rather it appears the back test is pulling stocks only currently in the watchlist.