NEW YORK (CNNMoney.com) - While investors focus on surging energy prices and confusing signs about interest-rate policy, first-quarter earnings have quietly been delivering in a big way.

Roughly 74 percent of the S&P 500 has reported earnings, with growth currently pegged at 13.8 percent versus a year ago, according to earnings tracker Thomson Financial. That's a blended figure, combining reported and expected earnings.

Granted, that's a far cry from the four-quarter stretch between the third quarter of 2003 and the second quarter of 2004, when S&P earnings jumped more than 20 percent in each quarter.

Nonetheless, the 13.8 percent figure - should it hold up through the end of the reporting period - would make the first quarter of 2006 the 11th in a row in which earnings have grown at least 10 percent. According to Thomson, there has only one other time since 1950 that corporate earnings grew at least 10 percent for 11 straight quarters, just before the tech boom of the late 1990s, in the period between the fourth-quarter of 1992 through the fourth quarter of 1995.

On average, companies are beating forecasts by about 5.1 percent, according to Thomson. That's above the 3.9 percent average surprise factor over the last 8 quarters and above the long-term historical average of 3.2 percent.

Granted, the number could come down a bit by the time all the reports are in, but even so, it will likely remain above the two historical averages, said Thomson research analyst David Dropsey.

Surprising no one, energy has shown the biggest year-over-year growth; it's currently expected to have grown 37 percent from a year ago, thanks to big profits from companies such as Chevron (Research) and ConocoPhillips (Research).

It was initially expected to have grown even more, but saw the overall expectation ratcheted down because of Exxon Mobil, which reported strong earnings that nonetheless missed analysts' forecasts.

The materials sector has been a stealth winner, going from initial forecasts for a decline in the quarter to a likely gain of 10 percent. (See chart)

That's thanks to stronger-than-expected results from DuPont (Research), U.S. Steel (Research), Newmont Mining (Research) and Alcoa (Research), said Dropsey.

"There aren't a lot of large materials companies in the S&P 500," said Dropsey. "But when you have DuPont and Alcoa doing that well, and surprises from the supporting cast, that's enough to lift the sector."

Both energy and materials look poised to lead the advance in the second quarter. Or as Dirk Van Dijk, analyst at earnings and research firm Zacks wrote in a note Monday, "the picture might be termed the revenge of the rustbelt."

Currently, S&P 500 second-quarter earnings are expected to rise 11.3 percent and third-quarter earnings are forecast to rise 15.2 percent, but Dropsey said that these numbers are likely to be revised higher.

Why is that? First of all, actual earnings tend to come in higher than the initial forecasts (See chart). Secondly, analysts' forecasts for the energy and materials sectors are likely to rise over the next few months, boosting the overall numbers.

Currently, energy earnings are expected to grow 22 percent in the second quarter and 9 percent in the third quarter.

"Analysts aren't expecting energy to remain at these levels through the year, but the longer crude stays near $75 a barrel, the more likely it is that they are going to need to revise their forecasts upward," he said.

For the fourth quarter, earnings are expected to rise 14 percent. In 2006, earnings are expected to rise 13.2 percent versus 2005, while 2007 earnings are currently on track to rise 10.7 percent from 2006.