It's not for lack of effort. The Federal Reserve has created more than $2 trillion in new cash to go out and buy assets, including U.S. Treasury debt and mortgage securities, in an effort to get things moving. Short-term interest rates have been near zero since 2008.

The government has spent trillions more on stimulus packages, from then-President George W. Bush's stimulus checks in 2007 to President Barack Obama's $787 billion package to the payroll tax cut approved in December. There was the $700 billion bank bailout. The American International Group (AIG, news) bailout. The automaker bailout. The Bear Stearns dowry to JPMorgan Chase (JPM, news). Cash for Clunkers. Cash for washers. The homebuyer tax credit. The federal takeover of Fannie Mae and Freddie Mac.

Yet through it all the economy has acted like a black hole, sucking in stimulus spending and cheap money and yielding very little in return. Each new effort, which carries ever-greater risk of inciting runaway inflation or a new government debt crisis, falls short. We can't resist the relentless gravitational pull of the Great Recession.

For investors, the advice is simple and echoes the recommendations I've been giving in these pages for months: It's time to get defensive. For most conservative, long-term investors, this means cutting your allocations to equities and bonds and moving into cash.

Time to move into cash