Isn't there a way to cut out outliers methodically to get a better picture of the majority? It's been a long time since I took statistics. I also think these numbers would change if you broke them down to regional or religion or other demographics. A single number for everyone doesn't tell the whole story.
My wife and I are 3 years apart. One of the things she liked when we were dating was that we had the same cultural references from childhood. She had dated men 10 years her senior and didn't like it for that reason.
At 26 I was hanging out with friends and this one girl was a cutie (who was clearly in her mid-twenties) that I was casually flirting with. Then she said "I gotta go, my dad's picking me up" and I'm like "Wait you don't drive?" and she's like "Dad doesn't want me to drive till I'm 18" and. I. Was. Mortified. I felt like a complete pedophile. God damned Latinas.
The point is, dating outside (x/2)+7 is unacceptable, but even over 40 a 10 year age gap is weird