Age 32 (almost 33)... $171k.
Started salary sacrificing in 2014 when my balance was about $50k.
My records suggest about $50,000 of the total balance comes from investment returns after fees and insurance, half of that since June 2017.
The graph attached has always ever only gone up - measured in 6 monthly periods - I've never had a 6 month period where the balance has declined. The last 6 months I had contributions of $13,500 but the balance only went up $550 due to the poor market returns. It's already bounced back quite strongly in the last two weeks (as I am heavily weighted to equities).
14 years of data is interesting, but it will be even more interesting to see it in 14 years time :)