 The effectiveness of condoms , as of most forms of contraception , can be assessed two ways . Perfect use or method effectiveness rates only include people who use condoms properly and consistently . <unk> use , or typical use effectiveness rates are of all condom users , including those who use condoms incorrectly or do not use condoms at every act of intercourse . <unk> are generally presented for the first year of use . Most commonly the Pearl Index is used to calculate effectiveness rates , but some studies use <unk> tables . 
