Missed it by THAT much: Why a fraction of a point is key for the S&P

Last week, the S&P 500 Index came close to closing above a key level. Actually, it didn't come close.

It came very, very, very close.

The S&P 500 rose 2.7 percent over the course of the week, and hit its highest level in nearly two months after a strong February jobs report. In Friday's session, it also crossed above the key level of 2,000, which has developed importance for both psychological and historical reasons.

Read MoreDow closes at 2-month high after jobs

It didn't close above that level, however. Instead the S&P 500 closed at 1,999.99 — or more specifically, at 1,999.98722585876.

Never before has the S&P 500's closing price been that close to a number divisible by 100. Before Friday, the S&P had never seen a "99.99" close, Howard Silverblatt, senior index analyst at S&P Dow Jones Indices, told CNBC.

Silverblatt adds that there have been two closes right at a 100.00 value, but not in a while. The two dates in question are October 25th, 1979 and July 28th, 1978 — with the index closing at 100.00 each time.

The bottom of a range

Fun facts aside, the market's reticence around this particularly level may be telling.

Frank Cappelleri has been keeping a close eye on 2,000 lately. A market technician and sales trader at Nomura-owned agency broker Instinet, Cappelleri says that "it's been a line on people's radar screens."

"Everybody knows it's there," he said. "It's psychologically important not only because it's a round number," he said, but also because it serves as the bottom of the market's trading range from mid-October to early January.

Based on Friday's close, it's likely a spot at which you see a short-term pause," Cappelleri predicted.

Chicago-based trader Brian Stutland is of a similar mind.

"There's no question that when you have a big number like that, everybody watches it," he said. "I wonder if people are anticipating that it gets to that point, and then takes a breather."

For Stutland, who has recently found himself taking a more bullish stance on stocks, 2,000 looks to be "a number we consolidate at before moving higher."

"Sometimes the market likes to find a nice, big, whole number to sit on and take a break before picking a direction — and right now, it looks like that number is 2,000," he said Friday.

Of course, the market is not managing to sit on it, exactly. For right now, the S&P is still 0.006 percent shy.

—By CNBC's Alex Rosenberg.

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