Are the salad days of higher and higher tanker rates, and ever-higher dividends, coming to an end -- at least for this economic cycle?

Nordic American Tanker Shipping (NYSE:NAT) is reporting today that it expects third-quarter earnings to be $0.25 to $0.29 per share. That's just a fraction of the $1.05 a share earned in the comparable quarter last year, and well south of the $0.40 to $0.65 the four analysts following the company were expecting. In late-afternoon trading, the stock is down 4.5%.

Oil tanker stocks had been riding high. Booming economic demand, especially in India and China, sent leasing rates skyward. Those rates in turn increased order rates for new ships at already capacity-constrained ship yards, which were previously expecting to scrap a significant percentage of the industry's fleet due to double-hull regulations taking full effect in 2010.

Nordic earned $0.57 a share in the second quarter, when the IMAREX Suezmax spot rate was $32,654 a day. The third-quarter average rate is $23,246 a day -- a significant drop that accounts for the company's current earnings shortfall.

Investors would be wise, however, to look at current and future Suezmax rates. On Sept. 22, the Suezmax spot rate was $29,216 a day -- a solid strengthening. Fourth-quarter rates are currently at $44,816 a day, so the future is not as gloomy as the stock's fall from $56.68 in February to $37.69 today might suggest.

Nordic and peers Frontline (NYSE:FRO) and TsakosEnergy Navigation (NYSE:TNP) pay healthy dividends, and their stocks, like Nordic's, are in the lower half of their 52-week trading ranges. Income investors should take a look at these stocks at current prices. Yes, the high yields are falling, but at expected earnings levels, the company will continue to pay above-market dividend rates. Unless economic activity cools substantially, it's my opinion that continued demand for oil should keep shipping rates at solidly profitable levels. The bottom line is that as investors, we need to be aware that shipping rates are as much a commodity as the goods they move. Investors would do well to buy at points when rates ease (barring a protracted economic slowdown), as stocks are prone to follow suit, pushing yields higher.

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Fool contributor W.D. Crotty does not own shares in any of the companies mentioned. Click here to see The Motley Fool's disclosure policy.