(The Wall Street Journal)--As the US stock market struggles, it is facing another head wind: Some of the nation's most powerful investors are unloading shares in a big way. Several of the largest public pension funds have been selling billions of dollars held in US stocks, and others are expected to join in.

In most cases these actions are unrelated to the recent market jitters, though worries about the economy, the weakening dollar and the credit crisis could be accelerating these moves. More broadly, they are part of a long-term plan to reduce stock holdings in US companies to help fund other investments.