Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

Although the thick of the holiday season is right around the corner, traders will certainly be glad to see the end of this week in which the S&P 500 (SNPINDEX:^GSPC) suffered its worst weekly losses in roughly a quarter.

The only noteworthy piece of economic data to hit the tape today was the November Producer Price Index, which decreased by 0.1% (core PPI rose by 0.1%, in line with expectations). With enterprise costs remaining under control there's little worry that we're going to see rising prices on the consumer side for at least the next couple of months -- and that's a good thing, with consumers being so skittish about their spending habits recently.

The S&P 500 wound up falling Friday, albeit fractionally, by 0.18 points (-0.01%) to finish at 1,775.32. It was the fourth consecutive day for losses on this index.

Leading to the upside today was struggling trucking company YRC Worldwide (NASDAQ:YRCW) which advanced 24.9% following word that its labor union had agreed to vote on extending an agreement that would allow YRC to attempt to refinance its debt. YRC CEO James Welch said the agreement would cut costs by $100 million annually, but wouldn't reduce any of the workers' pay or health benefits. If approved, the deal would be effective through March 2019. With rival Arkansas Best (NASDAQ:ARCB) recently ratifying a multiyear labor agreement that will dramatically reduce its costs, YRC needs to move quickly or its efforts to raise cash and avoid a possible bankruptcy may have been all for naught.

Specialty merchandise retailer Martha Stewart Living Omnimedia (NYSE:MSO) rallied to the upside by 18.4% following a New York Post report that the company had laid off 100 workers, or 20% of its workforce. Investors are cheering the move because layoffs mean lower general expenses (i.e., salaries) which can potentially help boost profits. The main problem, as I see it, is there are no clear-cut catalysts to push the Martha Stewart brand of products higher. Unless this company wrangles up some very lucrative partnerships over the next couple of months, I see no reason to chase the stock higher following today's pop.

Finally, cloud-based applications developer Adobe Systems (NASDAQ:ADBE) gained 12.8% after reporting its fourth-quarter earnings results. The actual results were nothing to write home about, with profits down 70% as revenue dipped 10%. The reason for the excitement, though, is Adobe's move toward a recurring revenue stream model, which does lend itself to short-term profit and revenue hiccups but positions the company for success over the long term. Adobe ended the quarter with an additional 402,000 Creative Cloud customers, bringing its cumulative total to 1.44 million, and delivered Marketing Cloud revenue growth of 38%. It appears that shareholders are caring less and less about Adobe's near-term results as long as it continues to pile on recurring-pay subscribers to its cloud-based platform.

Fool contributor Sean Williams has no material interest in any companies mentioned in this article. You can follow him on CAPS under the screen name TMFUltraLong, track every pick he makes under the screen name TrackUltraLong, and check him out on Twitter, where he goes by the handle @TMFUltraLong.

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