[teamhappy]

Realised that the second I pasted the text. It's midnight in Germany ... That's the original link I found: http://askville.amazon.com/AMERICAN-WOMEN-TAMPONS-PADS-PERIO...

And here is another statistic: https://www.ncbi.nlm.nih.gov/pubmed/22980411

They're both not clear though I do think it's fair to say tampons are preferred. Just google for "tampons vs. pads".