Big stock sell-offs emanating from bad corporate news tend to be one-day events. But not for Best Buy this week.

Shares in the nation's biggest electronics retailer fell again, dropping 9 percent Friday as investors continued to absorb the company's announcement Thursday of worse-than-expected sales during the holidays. The decline followed a 29 percent plunge on Thursday.

Over the two days, investors wiped 35 percent, or $4.6 billion, off the Richfield-based company's market capitalization, which stood at $8.4 billion Friday night.

It was the biggest two-day decline for Best Buy shares since Nov. 9-10, 2000, and just barely eclipsed a two-day fall of 34.8 percent on Aug. 7-8, 2002.

Friday's closing price of $24.43 left Best Buy shares at the cheapest level since April 29. Throughout 2013, Best Buy was one of the top-performing stocks of the S&P 500 as its shares tripled. Investors applauded the turnaround efforts made by new executives led by CEO Hubert Joly, who took over in September 2012.

On Thursday, Joly called the holiday results, in which comparable-store sales declined 0.9 percent, "a bump in the road." He reiterated previous statements that his strategy is "a long-term thing, two to three years." He added that he tells executives and employees "not to pay attention to the stock price" and to keep an eye on what they can control.

Best Buy didn't release any statements Friday, and there was little other news from the retail sector. A company spokesman had no comment after market close.

During trading Friday, Best Buy shares seemed unable to find a bottom. They ticked down 4 percent in the first half-hour, recovered slightly, then skidded steadily downward. The closing price was only two cents above the stock's lowest trade of the day.

The sell-off began after Best Buy announced Thursday morning that revenue at U.S. comparable stores, those open at least 14 months, fell 0.9 percent during the nine-week holiday sales period ending Jan. 4. Investors and analysts had expected a gain of 0.7 percent. Best Buy cited the toll of deep price discounting and lower-than-expected demand for cellphones for the drop.

Though executives warned in November that the holiday season appeared "increasingly promotional," the results immediately changed investors' views on Best Buy's recovery from its struggles in 2012 and reignited a debate about its ability to compete, particularly with online giant Other traditional brick-and-mortar retailers also struggled during the holidays against online competitors with lower costs.

Several analysts lowered their ratings on Best Buy shares to "neutral" after Thursday's news. Most retained "buy" ratings on the stock but with lower price targets for it.

An analyst at Bank of America bucked the trend by upgrading his rating on Thursday to "buy."

"At current levels, BBY still offers opportunity," the analyst wrote, using Best Buy's stock symbol.

And a few hours after trading ended on Friday, a Merrill Lynch analyst provoked a reaction on Twitter by issuing a new report on Best Buy with an upgrade to a "buy" rating. "May pop on Tuesday," one person with the Twitter handle of "trader j" wrote after taking note of Merrill's move.

The stock market is closed Monday for Martin Luther King Jr. Day.

Jim Foster contributed to this report.