WASHINGTON (MarketWatch)—Call it an August aberration. Wall Street really doesn’t believe hiring in the U.S. took a turn for the worse toward the end of the summer. Investors expect job creation to rebound sharply in September. And they believe a disappointing employment report in August will be revised to show more hiring than the government originally reported.

The latest employment report, released Friday, could help soothe jitters in stock markets if it shows that companies continue to hire at the fastest pace since the recession ended five years ago.

Also read: What the September jobs data are trying to tell us

Initial jobless claims probably can’t get much lower

What’s in the forecast

The U.S. probably created some 220,000 jobs in September after a preliminary 142,000 gain in August, according to economists polled by MarketWatch. The unemployment rate is likely to remain unchanged at 6.1%.

If the forecast is accurate, hiring would revert to the same rapid pace before the August surprise and ease lingering doubts about the labor market. The economy added an average of 226,000 jobs a month from January through July.

Yet don’t be shocked if Wall Street gets a similar jolt like the one it received in August.

September surprise

Employment growth in September is often below average compared with other months of the year, a trend that has been in place since the late 1990s. Some economists say seasonal adjustments in September are more difficult to make than in most other months.

In 2013, for example, the U.S. added 164,000 jobs in September vs. the monthly average of 194,000. And 161,000 jobs were generated in September of 2012—below the 186,000 monthly average for that year.

August redux

Investors will also pay close attention to a fresh estimate of job creation in August. Virtually every labor market indicator suggests the economy added more than 142,000 jobs in the last full month of summer.

Recent history supports the more bullish view. Since 2011, for example, employment growth in August has been increased by an average of 70,000 a month compared with the government’s first read.

Hourly wage growth

With job creation on the upswing, the pace of hourly wage growth could become the single biggest key to when—and how fast—the Federal Reserve raises interest rates. Wages have been growing at a 2% pace since the U.S. exited recession five years ago. That’s about two-thirds as fast as hourly wages have grown historically.

Theory says more hiring and a falling unemployment rate will reduce the pool of labor and force companies to offer better wages. So far that hasn’t happened, and the economy can’t grow much faster until it does.

Composition of hiring

A big reason wages haven’t grown faster is because the bulk of the new jobs earlier in the recovery were concentrated in lower-paying fields such as retail, hospitality and temporary work. A pronounced shift toward higher-paying jobs began late in 2013 and has intensified in 2014.

In August, for example, some 77% of the new jobs created were in fields that pay above the average hourly U.S. wage of $24.53 ($981 per 40-hour week, $51,020 a year). While that’s an unusually high percentage almost certain to fall, a sustained increase in good-paying jobs would eventually boost wages and drive the U.S. toward a faster rate of growth.