Note: I'm not going to count harmful acts that are "built-in". So if you play football and tackle a guy, it doesn't count as long as it's within the rules of the game.
The average US family is 2.58 people. Now, at some point in your life, you'll probably end up hurting your family members in some way. So that's 1.58 lifetimes. In addition, you'll likely have a family of your own once you grow up, so that's another 1.58 for 3.16. But that's just direct family - we also need to consider extended (cousins, aunts, etc). I think it's likely if you have contact with them, you'll end up causing some sort of harm to them, enough to trigger this. Let's call this another 1.58 bucket.
However, we also have divorce, and multiple families. The standard statistic is half of all marriages end in divorce, but not all of those will have children. Plus, not everyone will re-marry after. So let's just go ahead and round up our family number to 5.
I wasn't able to get good data on this, but some googling showed a decent number as ~5 boyfriends/girlfriends during a lifetime. In addition, I'm going to guess at another ~5 hookups/one-time sex partners.
My guess is that most relationships/breakups, at some point, will cause some sort of harm. And let's say that half of one-time sex ends up causing harm beyond the normal. So another 2.5, for 7.5 total.
This is another situation where most friends you have, you'll probably end up hurting emotionally at some point. Hard to find an average on this, but I'm pretty introverted and I still had ~10 so far. So I'm going to guess at ~30 for this number, which may be high but I also want it to cover acquaintances that you end up hurting.
Total Friends and Family: 30 + 7.5 + 5 = 42.5 lifetimes, or 3,315 years.
This is tricky because I think it will vary with regional - people in the south will probably spend a lot longer in hell for killing insects than people living in northern, colder areas. But I'll try to average it out. I'm ignoring flies here because they don't live very long and I don't think you end up killing or harming that many of them.
Spiders: Let's kill a spider once every 4 weeks, living an average of 6 months. So this will be 500 years.
Mosquitos: Depends on how long you spend outside. Most mosquito killed will be female, which live ~1 month. I'm going to call this 1 per 4 weeks, so 1,000 over your lifetime = 85 years as a mosquito.
Nests/Hives: This is trickier. Let's say that the average human will kill/harm two of these during their lifetime (WAG here). A wasp nest has 5,000 individuals that live about 6 months. A bee hive has ~70,000 individuals that live ~6 weeks. Ants vary widely, but let's call a nest 10,000 individuals that live ~8 weeks.
Average all that out and we end up at ~4,000 years per nest, so 8,000 years. Once we account for other insects and variations, let's go ahead and round this to ~10,000 years as an insect.
I don't know if this is accurate, but I'll assume all food animals are harmed at some point, even if it's just when they're killed (although I'm sure some of it is automated). As of 2014, in thousands:
- Cattle: 12,605 @ 2 years per
- Chickens: 3,542,950 @ 2 years per
- Ducks: 10,679 @ 8 weeks
- Pigs: 44,608 @ 6 months per
- Turkeys: 92,095 @ 6 months
I assume a US population of 320 million on average. Plugging that all into an excel spreadsheet and multiplying by 78 (since that's per year) we get 1,750 years total per person.
Let's say the average person has four pets in their lifespan, and nearly all of those will fit somewhere under the "harm" category (smacking a dog's nose, for example...). If the average pet lives 15 years (cats and dogs), that will be another 60 years.
US violent crime rate in 2010 was about 15 per 1,000 people. We can use this in our estimate since we're just looking for the average time spent in hell as a victim (Note: it's estimated that this is under-reported, but that's largely because of friends and family crime, which is already covered earlier).
Over 78 years, that will turn into 1170 / 1000. Which means that on average, violent crime will only add 1.17 lifespans, or 91 years to your hell.
- 3,315 friends and family
- 10,000 insects/spiders/icky
- 91 from crime
- 1,750 from food animals
- 60 pets
For a grand sum of 15,216 average years of hell, most of which is spent as a nearly mindless insect.
It might be interesting to consider the mode or median of the reincarnation hell, rather than the average/mean. For example, I suspect that even if the 2 nest/hives in a lifetime is accurate, probably the majority of humans will never destroy even one. This means that the most common length will probably be somewhere in the 4,000 - 5,000 year range. Then you'll have people with more and more years, largely depending on the number of insects they killed, with exterminators being hit the worst - one year of extermination work will probably net someone a million years of hell. It's also likely that people working with large scale farm animal operations are in for a rough time.
I also like that, in general, this means young children won't experience much. They don't have as much opportunity to hurt others, or as long of a period where they can have intent to hurt.
On the other hand, it's kind of weird that crimes we'd consider heinous - like a child killer - aren't punished as severely. If you kill a small child you might not experience much at all - just a few years - where the person who gave you a lethal injection gets your entire life, plus they have to experience killing a child as part of that.
Finally, one thing I considered here is that for the most part, when you kill/hurt things you cut their lifespan shorter. Take bees, for example - on average they live 6 weeks. But the average lifespan of a worker bee who lives in a hive that's attacked is probably shorter, because they naturally fall into the lower half of the sample size. So I think it's possible that some of these estimates are high, and maybe the insect numbers should be lower. But I don't have a great estimate for how much that should be reduced.