Well, not to alarm you, but I've been doing this since 1997, so, almost 6 times as long as you have and my numbers are ...
I contributed a little less than 30% of the total value of my retirement savings.
Lumping in my employer contributions (I've contributed a total of 65% of what's in there, my employer, 35%), I have slightly more than double what's been contributed over that time.
I've been close to fully invested in stocks over the duration during which there have been significant ups and downs in the market (I have not sold, or bought, to try to time anything, and my account's with TIAA-CREF, so reasonable account expenses).
I have pretty much always (with 2 years that were exceptions) contributed the maximum allowable, but that's increased over the interval in question; when I started, the most I could contribute was $10K and of course now it's $17.5K soon to be $18K. My employer match has gone up over time (changed employers); for the past decade or so they've been contributing almost half as much as I do (in the $8K range). So the over-time-rate-of-growth looks lower than it might, in the sense that more of that money I (and my employer) have put in, have been there for shorter amounts of time.
I was happy to see the balance in my account hit 200% of (total) contributions, and I do remember watching to see when it would happen -- but it was after 16 years of employment/contributing.