Which of the following methods of birth control has maximum failure rate?

Failure rate is high in natural methods of birth control (25% in periodic abstinence, 27% in coitus interruptus). The failure rate of intrauterine devices (typical use) is less than 1%. The failure rate of oral contraceptive pills (typical use) is 1% to 2%. The failure rate of vasectomy is 0.15% and that of tubectomy is 0.5%.