A suggested reason why there is a 20 percent failure rate in India:

Condoms designed to meet international size specifications are too big for many Indian men as their penises fall short of what manufacturers had anticipated, an Indian study has found.

The Indian Council of Medical Research, a leading state-run centre, said its initial findings from a two-year study showed 60 percent of men in the financial capital Mumbai had penises about 2.4 cm (one inch) shorter than those condoms catered for.

For a further 30 percent, the difference was at least 5 cm (two inches). A poor fit meant the prophylactics often didn’t do the job they were bought for, and led to some tearing or slipping off during use.