I had to dig for it but this a study that was referenced in articles mentioning the 100 to 1000 times higher statistics. http://science.sciencemag.org/content/3

I had to dig for it but this a study that was referenced in articles mentioning the 100 to 1000 times higher statistics. http://science.sciencemag.org/content/344/6187/1246752 http://science.sciencemag.org/content/344/6187/1246752