Many of us have no idea how effective (or ineffective as the case may be), different birth control methods actually are. Doctors will tell you the effectiveness rates of some birth control options based on their “Perfect Use” efficacy rates and for others, you will hear their “Typical Use” efficacy rates. Perfect Use efficacy rates, also known as "Correct Use", reflect what happens when a contraceptive method is used correctly all of the time. Typical Use efficacy rates, also known as "Actual Use", reflect what happens in the real world when we factor in human error in the first year of use of a method. The chart below shows the difference in Typical Use efficacy vs. Perfect Use efficacy rates in some of the most commonly used user-controlled family planning methods:
Note that "user-controlled" methods have a somewhat greater difference between Typical Use and Perfect Use efficacy than "doctor-controlled" methods such as IUD's and hormonal implants.