This matches textbook data too - Goldman-Cecil Medicine notes about 18% of women experience an unintended pregnancy in one year with typical condom use alone (Goldman-Cecil Medicine, p. 2719).

Bottom line: Condoms significantly reduce risk but are never 100% protective for either pregnancy or STIs. The gap between the "98% perfect-use" figure and the "82-87% typical-use" figure comes down almost entirely to human factors - putting it on late, incorrect storage, breakage, or inconsistent use every time. Using condoms correctly and consistently, and combining them with another contraceptive method (like an IUD or pills) for pregnancy prevention, maximizes protection.