NEW YORK (CNN/Money) - Convinced that things really are going to get better, investors have gone whole hog into the stocks of companies whose fortunes are most closely tied to the economy, while their enthusiasm for safer issues has waned. They may have gone too far.

Since the stock market hit its lows in March, cyclical companies -- whose earnings flow and ebb with the ups and downs of the economy -- have seen big rallies in their shares. High tech stocks in the S&P 500 have hopped 19.3 percent, industrials have risen 18.7 percent and the shares of consumer discretionary companies (which make the things you want to buy, but do not need) have risen 23.9 percent.

Meanwhile, the shares of companies whose earnings tend to maintain their growth even when the economy goes sour have not fared so well. The S&P health care stocks (you'll pay to stay healthy even in recession) are up just 12.5 percent. Consumer staples companies (which make the things you must buy even in tough times, like food and beer) have seen their shares rise only 7.5 percent.

This rush into cyclical companies is typical when investors believe things are going to get better. What's different this time, however, is that valuations on cyclical stocks are near (or over) the levels of the noncyclical ones. This doesn't make sense.

Consumer staples and the health care sector both have a P/E of 20. Getting awfully close, the S&P consumer discretionary stocks are trading at 18 times expected 2003 earnings and industrials also have a P/E of 18. Techs have a P/E of 33.

This would all make sense if the cyclical stocks offered close to the same kind of growth as the non-cyclicals. But they don't. Tech company earnings have averaged an 11 percent annual decline over the past five years, consumer discretionary companies averaged an 8 percent earnings decline and industrials saw average earnings growth of 5 percent.

In contrast, consumer staples saw average earnings growth of 12 percent and health care companies' earnings growth averaged 11 percent.

Even if you exclude the last couple of tough years, cyclical companies' earnings growth doesn't look so hot. For the five years ended in 2000, consumer discretionaries and industrials saw average growth of 8 percent, and techs saw growth of 11 percent.

Something's not right here. Either noncyclical stocks should, because of their steady growth, be trading at richer valuations, or cyclical stocks should go lower.  

-- Justin Lahart is a senior writer at CNN/Money covering markets and investing.