WASHINGTON — The news that the economy added just 96,000 jobs in August will be hotly debated by both sides in remaining weeks of the presidential campaign, but one thing is almost certain: The number is wrong.

Only once in the past three decades has the government not revised its estimate of how many jobs were created in a given month. It usually takes many weeks, and sometimes years, before economists settle on the most accurate figure.

Over the past three years, the employment report has understated how many jobs were created by as much as 99,000 and overstated it by as much as 86,000. The nation dwells on the number when it comes out, but nobody pays attention when the number is updated.

Although the figure released Friday morning is highly unlikely to be correct, it does confirm a trend of tepid job growth and suggests that the economy is neither collapsing nor growing vigorously. But history may reassess how much of a setback the disappointing figure was for President Barack Obama.

At precisely this time last year, Obama learned the lesson the hard way. It was Thursday, Sept. 1, and the President's senior economic team had just heard the details of the August jobs report. The jobs number, made available to a few government officials ahead of the public release the next morning, was a scary one.

Gene Sperling, the director of the National Economic Council, and Katharine Abraham, a member of the Council of Economic Advisers, headed to the Oval Office. There, they told Obama how many jobs were created in August: zero.

The next day, Obama was called “President Zero” by his critics. It was a painful coda to a difficult summer when the nation flirted with a default on the government's debt. Sperling and other advisers used the news to successfully make the case for boosting the president's jobs plan — to be unveiled in Congress just a few days later — by $75 billion.

But the number was wrong. After the government revised its data three more times, it concluded that 84,000 jobs were created in August 2011.

That wasn't a great number by any means. The economy needs at least 120,000 jobs per month just to keep up with population growth. But it also meant that much of the political fallout in the following days was based on the wrong number.

Friday's report of 96,000 jobs added in August will be used the same way, fairly or not, to judge Obama's record. In October, when the first revision of the August number is made available, a jobs report for September will be announced, and that will move to the center of the political debate.

“The initial number is important, but the data the initial number is based on are incomplete, so the number will be revised as soon as next month, and will be revised with much more complete information after the election,” Tara M. Sinclair, an economics professor at George Washington University, said in an email.