162: Number of months it would take at this year’s pace of job growth for unemployment rate to fall to 5%.

U.S. employers have added 757,000 jobs to their payrolls in the first half of this year. That actually wouldn’t be so bad if there weren’t so many people out of work. The June unemployment rate of 9.2% was well above the 5% it logged in December 2007, when the recession got under way.

What would it take to get the unemployment rate back down to 5%? Much stronger growth in jobs — or a whole lot of time. Here’s a back-of-the-envelope calculation:

The unemployment rate, based on a Labor Department survey of households, is the share of the work force (people with jobs plus people seeking jobs) who are unemployed. Out of a workforce of 153.4 million people, there were 14.1 million unemployed in June.

The Labor Department’s payroll figures are based on a separate “establishment” survey of employers that doesn’t include some workers, like farmhands, included in the household tally. To get around this, assume employment in the household survey increases at the same rate as employment in the employer survey did in the first half of 2011. That implies a gain of 1.2%, or about 1.6 million employed, over the next year.

Next, we have to factor in labor force growth. If we assume that it grows at the same pace as the Census projects for the working age population – people aged 16 and over – it will increase by about 1.4 million people next year. With employment growing just a smidge faster than the labor force, then, the unemployment rate would still be a disappointingly high 8.9% in June 2012. The October 2012 unemployment rate — the last one we’ll see before Election Day — it would edge down to 8.8%. And it wouldn’t reach 5% until December 2024.