You're still missing the point.

When a person sees abortion as murder, the view of abortion laws is the same as those of murder. If you say "making murder illegal doesn't reduce the number of murders" anyone with any sort of a moral center will say "I don't care, murder should still be illegal." And that's the perspective will not be changed no matter what the murder rates are. That's how the argument gets reduced to "Why have laws?" To them, it's basically saying "It doesn't help enough, so why even draw that line at all?"

That said, let's look at your proven fact for a moment. I don't believe the data will help, because when you narrow the focus to the US, and look at reaction to legal changes, you see a very clear drastic rise in abortions in the 70's, which didn't begin to fall until the 90's, and it fell at a much slower rate, and is still higher than it was in the 70s. ( source )

Which makes logical sense, if you increase access to the service, of course more people will be able to use it. At the same time, since Roe vs. Wade was repealed, there have already been multiple news stories showing that the strict abortion laws did prevent some (often medically necessary life-saving) abortions.

You may say these numbers aren't statistically significant, but to a person who sees abortion as murder, preventing even one is better than not preventing it.

Anyway, all of this misses the major point of the abortion rights side to begin with. Which is that sometimes abortions are medically necessary and that should be between you and your doctor to decide when that is.

I want to say that the most effective argument is to show just how drastically the abortion rates fell in the areas where they increased access to birth control and sex education. However, when I showed my mother, she responded with a Youtube video that tells me how Planned Parenthood eats babies.