https://www.optionsforsexualhealth.org/birth-control-pregnancy/birth-control-options/effectiveness
- Use Effectiveness: How well a birth control method works in ”typical use”, taking into consideration human error and other non ideal factors.
- Theoretical Effectiveness: How well a birth control method works when it is used correctly and when all other conditions are ideal “perfect use”.
"To make an informed choice, both partners need to understand how to use the method correctly and consistently. Effectiveness figures are based on 100 couples using the method for a year and show the percentage of women who do not get pregnant while using the method for 1 year."
Condoms are 85% effective, leaving a 15% margin of error. If you're doing a lot of fucking, there might be a mistake. You think that mistake should lead to an unwanted child?