Contributions are included, as (I think) are realized gains; but a lot of the balances are unrealized gains, which aren't included.
Here's an example: over the last ten years, you've put the maximum into your 401(k); that's probably something like $40k pre-tax, which means you "think" you put away about $25k. But your balance shows over $120k, so you "think" you've put away 5x more than you really have.
I think the psychology goes like this: the limits on contributions (especially in earlier years) meant that people put away less than they might have otherwise, but with tax preference, there's an immediate "gain" (your check goes down $65 but your balance shows $100). As time goes on, contributions have less impact on the balance and unrealized gains can dominate the account. The gains have removed their interest in "making up" for the earlier smaller contributions, and they begin to focus on the balance rather than the rate of savings.
Opinions differ on whether this is a negative; mine is that tax policy in the US has shifted what "national savings rate" means to the point where it can't really be compared around the world. So it's one of those misunderstood terms that people use to get their point across: MY GOD, THE SAVINGS RATE IN THE US IS AT AN ALL-TIME LOW!!!
I'm not sure what point they are trying to make.
/jordan