Interesting article by Shang-Jin Wei (Wei Shangjin?), an economist at Columbia University in New York:

Our study compared savings data across regions and in households with sons versus those with daughters. We found that not only did households with sons save more than households with daughters on average, but that households with sons tend to raise their savings rate if they also happen to live in a region with a more skewed gender ratio. Even those not competing in the marriage market must compete to buy housing and make other significant purchases, pushing up the savings rate for all households.

Seems to argue that Chinese savings rates are a product of the gender imbalance, and that families with sons have to save more to help their sons compete on the marriage market. There's a really interesting graph about halfway down the page. Another tidbit:

Instead, the evidence that we find more compelling is that savings by otherwise identical households with a son are greater in regions with a higher local gender ratio. This is something clearly predicted by our hypothesis, but not by any other existing explanations. In addition, we find that savings by households with a daughter do not decline in regions with a high gender ratio.

Not sure how I feel about the argument. Plenty of food for thought though.