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.

This year is shaping up to be the least volatile we've seen in practically two decades. Moves like we saw in the broad-based S&P 500 (SNPINDEX:^GSPC) today certainly aren't going to help that cause.

One bright spot amid today's carnage was weekly initial jobless claims, which fell 15,000 to a seasonally adjusted 320,000 -- a six-year low. Fewer claims are a strong signal that the jobs picture is improving. However, many of the jobs being created are part-time, not full-time, which may not ultimately help consumer discretionary spending, which is the cornerstone of U.S. GDP growth.

The real reason for the bloodbath on Wall Street comes from disappointing news from Cisco Systems and Wal-Mart (NYSE:WMT). Cisco shares dove after announcing an additional 4,000 job cuts, while Wal-Mart led all indexes lower after delivering an unexpected same-store sales decline of 0.3% in the second quarter, and it's fifth-straight quarterly revenue miss. Wal-Mart also lowered its full-year revenue and profit forecasts for the year.

Cisco is viewed as a tech bellwether, so job cuts, as opposed to top-line expansion, won't be viewed positively by investors. Similarly, Wal-Mart, the U.S.'s largest employer, is often viewed as a health barometer of the U.S. economy. A tapering in same-store sales figures in a non-tax refund quarter could suggest that consumers' incomes are being affected more than we think by the removal of the payroll tax holiday.

Add on the fact that 10-year Treasuries hit their highest levels in two-years, possibly signaling another mortgage rate hike is around the corner, and you have more than enough reasons why the S&P 500 plunged 24.07 points (-1.43%). to finish at 1,661.32. This marks the seventh time in the past nine sessions the S&P 500 has closed lower.

Near the head of the pack amid one of the worst days of the year was none other than struggling retailer J.C. Penney (NYSE:JCP), which gained 5.5%. The move up for Penney's comes on word that billionaire investor George Soros had increased his stake in Penney's over the past quarter, as two other large funds liquidated their positions in the company. Penney's also received positive commentary from research firm Sterne Agee, which reiterated its buy recommendation and $23 price target on the company, with the risk-versus-reward ratio improving as we near its second-quarter earnings results. I still fail to share Sterne Agee's optimism, and would suggest shareholders keep to the sidelines until we see some semblance of stabilization in Penney's top- and bottom-line numbers.

What was a real surprise was that the top performers today came from the homebuilding industry, where a reading from the National Association of Homebuilders notes that homebuilder sentiment rose to 59 in July. Anything above 50 is considered positive, and 59 would mark the highest reading we've seen in six years. The news sent shares of America's largest homebuilder, D.R. Horton (NYSE:DHI), and the homebuilder with the beefiest margins, Lennar (NYSE:LEN), higher by 5.7% and 5.1%, respectively.

To me, though, the move higher seems a bit unjustified given the precipitous drop in mortgage applications since early May and the fact that Treasury yields, which often dictate 30-year mortgage rates, are heading higher. Compound that with the Federal Reserve potentially paring back its monthly bond-buying program before the year is out, and you have a recipe for disaster for the homebuilding sector.

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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