The negativity continued on Wall Street and with the broad-based S&P 500 (SNPINDEX:^GSPC) today following two economic reports that came in weaker than expected.

First, the Producers Price Index for February fell 0.1% against expectations for a rise of 0.2%. This was also down from an increase of 0.2% in January. Although falling prices for input costs can be viewed positively from a business standpoint, they can also signal deflation which would be bad news for the U.S. economy.

The other report of interest was the Thomson Reuters/University of Michigan consumer sentiment index which came in with a reading of 79.9, down from a prior reading of 81.6 and modestly below expectations. A lower reading here suggests that consumers are less confident about their short-term and long-term financial outlook. We want this figure to stay as high as possible since a confident consumer will buy consumable goods and drive GDP growth.

By day's end the S&P 500 limped to its second-straight loss, this time of 5.21 points (-0.28%), to finish at 1,841.13. It was down nearly 2% for the week.

Nonetheless, some stocks had a very good day. Independent oil and gas exploration and production company VAALCO Energy (NYSE:EGY) shot higher by 19.1% to lead all stocks to the upside after announcing its fourth-quarter results. For the quarter, VAALCO delivered $58.2 million in revenue, a 9% increase over the year-ago quarter, as it turned a year-ago loss of $0.33 per share into an earnings-per-share profit of $0.46. By comparison, Wall Street had only expected a profit of $0.34 per share. Although costs have been rising, the company's microscopic forward P/E of six, as well as its opportunities in Angola, gives me hope that it could head even higher.

Clinical-stage biopharmaceutical company Rigel Pharmaceuticals (NASDAQ:RIGL) also impressed with a gain of 15.5% despite no company-specific news, at least today. Shareholders appear to still be riding high on last week's publication in the American Journal of Physiology of select preclinical study results for its oral AMPK activator R118. The study noted that R118 could be useful in treating peripheral artery disease which affects millions of people in this country, potentially giving R118 enormous marketing potential if successful. Investors, though, will want to keep in mind that this is merely preclinical data, and R118 has a long road ahead before we should even consider putting a premium on Rigel's share price.

Finally, struggling Brazilian steelmaker Companhia Siderurgica Nacional (NYSE:SID) (say that three times fast!) surged 12.6% after announcing plans to repurchase up to 70.2 million shares of its common stock between today and April 14. The move is being made to bolster shareholder value after the company's share price has swooned by 39% from the beginning of the year into yesterday's close. Brazil's economy has been a bit choppy of late in the growth department, which makes me worry that that today's pop in Companhia Siderurgica Nacional may only be temporary. I would rather let the company's sales and earnings growth do the talking instead of being swayed by cost-cutting and share buyback incentives.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.