Amazon provides an Order History Export function and it will give you everything back to 2006 in a CSV download. I dumped that into a Google Sheet, did a quick pivot table to get orders by year...just because.
Now, a few caveats...
- This is only orders on my account, not our total household orders.
- I would haven't to manually enter orders prior to 2006 and I'm pretty lazy, so that probably won't happen.
- I don't know why our orders exploded in 2011. I should probably look up some kind of Amazon Prime timeline to see what launched.
- I don't know what happened in 2017.