BoardGameGeek allows people to keep track of which games they own. It's a useful feature that I use myself, and when meeting up with someone else you can always say 'Look at my BGG collection - is there anything of mine you fancy playing?' which is pretty cool too.
I know exactly how many games I've sold to distributors, but I don't know how many of those the distributors have sold to shops, nor how many of those the shops have sold to gamers. They same follows with direct sales to shops. A tiny fraction of my sales are direct to a gamer, so I know those have gone to gamers, but that's not much as a fraction of total sales.
Why am I interested? A game sold to a distributor that ends up sitting in their warehouse for months isn't doing me any favours at all. The distributor will be less inclined to buy more stock as it's costing them money (in the initial outlay to me and warehousing space) but not making them any. Similarly a game that ends up sitting on the shelf for a long time in a shop won't convince the shop to get more stock in. In the ideal world the game is in the hands of a gamer who loves it and plays it regularly with their friends.
It's hard to work out where the games are. I can ask my distributors how much stock they have left, but that still leaves me unsure whether the games are in the hands of shops or gamers. In the case of direct sales to shops things are a little better as I can ask them how many they've got left, but in that case again it's only a small proportion of the total sales at my end.
Here's where BGG's stats come in handy. The people listed as owning the game are gamers. So I can get some indication of how many of my sales to shops and distributors have reached actual gamers.
Of course, as with anything statistics they can't be relied on as a final number, but they are indicative. There will be people who've bought one of the games and don't have a BGG account, and others who do have BGG account but don't bother keeping track of the games they own. However, almost everyone who lists themselves as own a game will have it (some people might do it by accident or forget to remove it from their collection if they sell or trade it away).
Because I made a couple of small runs of Border Reivers and It's Alive! which almost entirely sold directly to gamers, I've got an idea about the ratio of gamers who list themselves as owning a game to the number of end customers I've sold it to.
If you look at the stats for Border Reivers (100 copies made) then it lists 42 people as owning it - 42% of the copies in circulation. Similarly, when I had sold out of the limited edition of It's Alive! about 110 people listed it as owned of the 300 copies made (37%). So I reckon I can extrapolate that about 40% of the copies in gamers' hands are listed as owned on BGG.
Assuming that 40% figure is evenly vaguely accurate, then approximately half the copies I've sold of the second edition of It's Alive! are in gamers' hands, and it's also about half for Carpe Astra. Sumeria (which is still fairly new) is around one third. Not sure what to do with this information, but it's interesting nonetheless.