The Tens Rule also known as the ten-ten rule describes the chances of an invasve species become established in an introduced environment. It states that 1 out of ten imported species appear in the wild and that of those 1 out of 10 will become established in that environment. It has been changed more recently to add three stages. They are escaping, establishing, and becoming a pest (1).
The Tens Rule has been said to be dangerous because it lends itself to the idea that invasive species are less damaging then they really are. The general public might see these numbers and dissmiss the threat of invasive species. Not all invasive species are recognized as pests, some of them have indirect effects. This isn't a perfect rule just a general guideline (2).
(1) Williamson, M., & Fitter, A. (1996). The Varying Success of Invaders. Ecology, 1661-1661. Retrieved April 14, 2015, from http://www.reabic.net/publ/Williamson_Fitter_1996.pdf
(2) Jarić, I., & Cvijanović, G. (2012). The Tens Rule in Invasion Biology: Measure of a True Impact or Our Lack of Knowledge and Understanding? Environmental Management, 979-981. Retrieved April 14, 2015, from http://www.ncbi.nlm.nih.gov/pubmed/22996401