How about an attach rate chart?

[Entroper]

Quartz said: Depends what you mean by 'attachment' rate.

Attach rate is a business term that represents the number of additional SKUs you can 'attach' to a main SKU. So if you sell an Xbox 360 with three games, your software attach rate is 3. At launch, this is something you can measure based only on sales data. After launch, new games will come out, and there will be people buying software who already have a 360, but you can still measure essentially the average number of games sold per console. If you do it cumulatively, you see how many games the average owner of that console owns. That's what's shown in those two charts I posted.