They are one form of long-acting reversible contraception which are the most effective types of reversible birth control.[60] Failure rates with the copper IUD is about 0.8% while the levonorgestrel IUD has a failure rates of 0.2% in the first year of use.[61] Among types of birth control, they, along with birth control implants, result in the greatest satisfaction among users.[62] As of 2007, IUDs are the most widely used form of reversible contraception, with more than 180 million users worldwide.[63]