Stop squandering my inheritance!

(Money Magazine) -- Getting old brings a host of changes. Achy knees. Way more time to play bridge. And, occasionally, the tendency to make unwise money decisions.

For example, Mom insists on keeping the obscenely expensive membership to a country club she can't afford and never visits, or Dad digs into his retirement stash to shower diamonds and vacations on a girlfriend half his age. You're left watching your inheritance dwindle even as you struggle to pay your kids' tuition.

The direct approach -- asking your parent to stop spending like Donald Trump, already -- is likely to back-fire. Who wants his child telling him what to do? It will also make you look like even more of a gold digger than Dad's new squeeze.

Economists have a remedy. Years ago three of them -- B. Douglas Bernheim, Andrei Shleifer, and Lawrence H. Summers (the guy who now advises President Obama) -- wrote a now classic paper called "The Strategic Bequest Motive."

After analyzing reams of data, they concluded that bequests are really trades. People generally want something in return for making them -- namely, time and attention. For example, studies show that children who frequently call and visit their elderly parents tend to inherit larger amounts than those who don't.

So the best way to stop your folks from frittering away their money is simply to shower them with love and devotion.

Whether consciously or not, they will treat their money more carefully because they'll want to leave it to you. Isn't it nice when self-interest and doing the right thing are one and the same?