That chart is kinda misleading ... people think it means "oh, condoms only work 98% of the time," and think that condoms fail once every 50 times even if used correctly.
It means that couples who have sex regularly for a year have a 2% chance of getting pregnant if they correct use a condom every time. The odds of getting pregnant with a single sexual encounter while using a condom are far less than 2%.
Let me add that I'm fully aware you didn't try to make the "2% of the time you still get pregnant with a condom!" argument, but people on your side make that false argument pretty often, so I felt the need to point it out.
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