International Business Machines Corp.’s stock had a day that will stand out in history books, as the company formerly known as Big Blue shocked investors with the best earnings report they have seen in nearly nine years.

The stock IBM, -1.72% rocketed $12.99, or 8.9%, Wednesday to the highest close in nearly six months, after the information technology company reported third-quarter profit and revenue the beat Wall Street expectations. It had run up as much as $14.69, or 10.0%, in intraday trade.

Beating profit projections wasn’t a surprise, since IBM has now done so for 12 straight quarters, but the stock rallying after results is a relative rarity. And Morgan Stanley analyst Katy Huberty said the latest beat marks “a real inflection point,” as it came amid “low investor expectations” and helps support the belief that the gross margin trend is now rising.

“Importantly, our quant analysis suggests IBM shares outperform the technology market on improving market trends,” Huberty wrote in a note to clients.

FactSet, MarketWatch

IBM’s stock was still down 3.9% year to date, while the SPDR Technology Select Sector exchange-traded fund XLK, -1.72% has surged 26% and the Dow Jones Industrial Average DJIA, -0.87% has advanced 17%.

Huberty reiterated her overweight rating and $192 stock price target. Meanwhile, the average rating of 27 analysts surveyed by FactSet is the equivalent of hold, and the average stock price target is $161.

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The following provides some historical perspective for how well IBM’s stock performed Wednesday:

• The stock’s one-day post-earnings percentage gain was the biggest since Jan. 21, 2009, when it rallied 11.5% after IBM reported fourth-quarter 2008 results. On the days after the 34 quarterly reports since then, before late-Tuesday’s report, the stock had only gained nine times by an average of 3.1%. The gains ranged from as little as less than 0.1% to as much as 5.7%.

• The one-day percentage rise was the ninth biggest this millennium, and the 18th biggest in the stock’s history, according to an analysis of FactSet data.

• The price gain was the second biggest in its history, just behind the biggest price rally of $13.50 on July 20, 2000. It was only the fifth double-digit gain in its history.

• The price and percentage gains are by far the biggest since Virginia “Ginni” Rometty became chief executive officer on Jan. 1, 2012. The previous biggest percentage gain during her reign was 4.4% on Jan. 20, 2012, while the previous biggest price gain was $8.64 on Jan. 23, 2013. Since Rometty became CEO, the stock has declined 13% while the Dow industrials have surged 89%.

• That price gain is adding about 89 points to the Dow industrials’, which was climbed 160 points to a record close.

• IBM’s stock entered the Dow on June 29, 1979. Since then, it has run up nearly ninefold, while the Dow’s price has been multiplied by 27.5.