A standard U.S. rule of thumb puts the real GDP growth needed to halve unemployment at roughly 12% in one year, or 7% annually over two years, assuming unemployment starts at 9% to 10%.

This estimate follows from Okun’s law: annual GDP growth about 2 percentage points above potential growth is associated with a 1 percentage point decline in unemployment. Potential growth reflects rising productivity and a growing labor force, so some growth is needed just to keep unemployment steady. [Federal Reserve explanation](https://www.federalreserve.gov/newsevents/speech/bernanke20120326a.htm)

Using the San Francisco Fed’s 2010 estimate of 2.5% annual potential growth gives:

\[
\text{Required annual real GDP growth}
\approx 2.5\%+\frac{2(u_0-u_{\text{target}})}{T},
\]

where unemployment rates are expressed in percentage points and \(T\) is the number of years. [Janet Yellen’s February 2010 speech](https://www.frbsf.org/news-and-media/speeches/yellen-speeches/yellen-outlook-economy-monetary-policy/)

With December 2010 as the starting date, the estimates are:

| Target | Time available | Starting at 9%, targeting 4.5% | Starting at 10%, targeting 5% |
|---|---:|---:|---:|
| December 2011 | One year | 11.5% growth | 12.5% growth |
| December 2012 | Two years | 7.0% annually | 7.5% annually |

Policymakers made similar calculations at the time. In May 2010, Boston Fed President Eric Rosengren estimated that reaching 5% unemployment by the end of 2013 would require real GDP growth averaging about 5% annually over the available period. [Speech and supporting slides](https://www.bostonfed.org/news-and-events/speeches/considering-the-routes-to-a-policy-destination.aspx)

The estimates depend on how closely the economy follows Okun’s law. This empirical relationship deviated substantially during the Great Recession, and changes in productivity, hours worked, and labor-force participation can affect how much unemployment falls for a given amount of growth. The figures therefore give an approximate guide to the growth needed, with no guarantee that it would produce the target unemployment rate. [San Francisco Fed analysis](https://www.frbsf.org/research-and-insights/publications/economic-letter/2010/03/okun-law-unemployment-2009/)