What a difference a year makes!

During the first half of 2008, as you may know, Halliburton (NYSE:HAL), the second largest of the oilfield services companies, rode a record run-up in global crude prices toward a similarly record year of its own. But on Monday, the company’s reported earnings slid down on a "significant volume reduction" and a "margin compression," and it was hit by a 35% year-over-year cut in its net income.

For the quarter, the company checked in with net income of $378 million, or $0.42 a share, compared to $580 million and $0.63 a share in the first quarter of 2008. Revenues were down 3% to $3.91 billion. However, excluding one-time charges, Halliburton was able to beat analyst per-share estimates.

The primary culprit in the company's earnings decline was North America -- the U.S. and Canada -- which experienced a 30% rig count decline from a year ago. This newfound overcapacity was a major factor in Halliburton's operating margin slide to below 16% from about 21% a year ago. Indeed, operating income fell 53% in North America, and during the call with analysts, the company noted it could still see another 300- to 500-basis-point drop.

So this was largely a geography thing. Revenue from the Eastern Hemisphere was about flat from a year ago, with strength in Africa generally offsetting a pullback in Russia. Nevertheless, the leader of the parade was Latin America, where ol' Halliburton benefited from strong activity in Mexico, Brazil, and Columbia.

According to the company's capable CEO, Dave Lesar, solid activity south of the border is likely to continue at least through 2009. He noted, however, that overall the current downturn differs from its predecessors because it's overlaid by the credit crisis.

Typically, reporting from the oilfield services sector is led off by the biggest of them all, Schlumberger (NYSE:SLB) and its words of wisdom from CEO Andrew Gould. But this time, the big enchilada will tell us about its results on Friday.

On Monday, Weatherford (NYSE:WFT) also reported sour results, and on Thursday it'll be Diamond Offshore's (NYSE:DO) turn out of the box. Next week, Baker Hughes (NYSE:BHI) will report, although with the operators cutting projects right and left, my expectations aren't high for any of the service providers. By then, we should have a better handle on the sector.

For that very reason, I'd let investment time horizon dictate your commitment to the services companies. If you have at least three years, perhaps think about taking a plunge. But if you're on a shorter leash, there are better places now to park your pesos.

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Fool contributor David Lee Smith doesn't own shares in any of the companies mentioned above. He does, however, welcome your comments, questions, or kibitzing. The Fool has an ironclad disclosure policy.