WASHINGTON — U.S. employers added 171,000 jobs in October, and hiring was stronger in August and September than first thought. The solid job growth showed that the economy is strengthening slowly but consistently.

The unemployment rate rose to 7.9 percent from 7.8 percent in September. That was mainly because many more people began looking for work, and not all of them found jobs. The government uses a separate survey to calculate the unemployment rate, and it counts people without jobs as unemployed only if they’re looking for one.

Friday’s report was the last major snapshot of the economy before Tuesday’s elections. It’s unclear what political effect the report might have. By now, all but a few voters have made up their minds, particularly about the economy, analysts say.

Since July, the economy has created an average of 173,000 jobs a month. That’s up from 67,000 a month from April through June. Still, President Barack Obama will face voters with the highest unemployment rate of any incumbent since Franklin Roosevelt and slightly higher than the 7.8 percent on Inauguration Day.

The work force — the number of people either working or looking for work — rose by 578,000 in October. And 410,000 more people said they were employed. The difference is the reason the unemployment rate rose slightly.

The influx of people seeking jobs “could be a sign that people are starting to see better job prospects and so should be read as another positive aspect to the report,” said Julia Coronado, an economist at BNP Paribas.

Investors initially were pleased by the news. When trading began an hour after the report was released at 8:30 a.m. EDT, stocks declined slightly.

The yield on the benchmark 10-year U.S. Treasury note climbed to 1.77 percent from 1.72 percent, a sign that investors were moving money out of bonds and into stocks.

Friday’s report included a range of encouraging details.

The government revised its data to show that 84,000 more jobs were added in August and September than previously estimated. August’s job gains were revised from 142,000 to 192,000, September’s from 114,000 to 148,000.

The job gains in October were spread across industries. And the percentage of Americans working or looking for work rose for a second straight month, to 63.8 percent. In August, the percentage had hit a 31-year-low of 63.5.

The economy has added jobs for 25 straight months. There are now 580,000 more than when Obama took office.

But there were also signs of the economy’s persistent weakness. Average hourly pay dipped a penny to $23.58. In the past year, pay has risen just 1.6 percent. That has trailed inflation, which rose 2 percent.

Because more people sought jobs than found one, the number of unemployed rose 170,000 to 12.3 million. That pushed up the unemployment rate.

The October jobs report was compiled before Superstorm Sandy struck the East Coast earlier this week and devastated many businesses.

The nascent housing recovery is finally generating jobs. Construction companies added 17,000 jobs, the most since January. Manufacturers added 13,000 jobs after shedding 27,000 in the previous two months.

Professional services such as architects and computer systems providers also added jobs. So did retailers, hotels and restaurants, and health care. Government overall shed 13,000 jobs, after three months of gains.

The economy has shown many signs of picking up a bit. Americans are buying more high-cost items, like cars and appliances. Auto companies reported steady sales gains last month despite losing three days of business to the storm in heavily populated areas of the Northeast.

Yet businesses remain nervous about the economy’s future course. Many are concerned that Congress will fail to reach a budget deal before January. If lawmakers can’t strike an agreement, sharp tax increases and spending cuts will take effect next year and weaken the economy.

American companies are also nervous about the economic outlook overseas. Europe’s financial crisis has pushed much of that region into recession and cut into U.S. exports and corporate profits.