The stock market is churning toward a correction, perhaps in the range of 5 percent to 10 percent. Behind this churn downward is the dollar's adjustment upward. And it's nothing for shareholders to fret about. In fact, with the economy so hot, it's a great opportunity for investors to fatten their portfolios -- and also a good time to reflect on why the economy is doing so well, and what will keep it going. Since mid-February, the greenback has risen about 4.5 percent relative to the yen and 5.5 percent versus the euro. This is likely the beginning of a...