I agree that that would have been the best way to measure the effect of the plug. But that wasn't an experiment, I just wanted to get as many readers as possibl

I agree that that would have been the best way to measure the effect of the plug. But that wasn't an experiment, I just wanted to get as many readers as possible; the idea to measure the effect of the plug only came later (actually, it was suggested in a comment here on HN).