IN OTHER WORDS, IT'S NEARLY USELESS AS A MEASURE:

Americans Are Finally Saving. How Did That Happen? (RON LIEBER, 12/20/09, NY Times)

But first, a bit about that savings rate — and the money that may feel like savings to you that doesn’t actually count when the government computes it.

The personal savings rate calculation begins with personal income and then subtracts taxes to determine disposable personal income. Both employee and employer contributions to 401(k)’s count toward the savings result, though data on employer matches can be a bit out of date.

Any capital gains, whether sitting in a brokerage account or realized through an actual sale of stock or mutual funds, don’t count, though. Also, while you may consider your mortgage payment a form of forced savings, the bit of equity you’re building up (when your mortgage isn’t underwater, at least) isn’t counted in the personal savings rate either.