As you'd expect the contribution percentage increases with age (and the amount presumably increases even more). But even under 25s are at about 5% which is more than I would have expected though this is presumably just among people who have the option.
"The market is like a large movie theater with a small door. And the best way to detect a sucker is to see if his focus is on the size of the theater rather than that of the door." - Nassim Nicholas Taleb in Skin in the Game
(This is not to say that you, specifically, are a "sucker", and I don't love the term. But I think Taleb has a lot to offer on considering risk.)
You're looking at market cap when you should be looking at volume. 5% of the stock market going liquid at a higher than ambient rate can reduce valuations by significantly more than 5%, possibly multiples more. And as we saw with interest rate hikes and bonds the past couple of years, something like that is a systemic risk and the fallout can easily cascade.
As you'd expect the contribution percentage increases with age (and the amount presumably increases even more). But even under 25s are at about 5% which is more than I would have expected though this is presumably just among people who have the option.