Forgetting a key fact or figure is a nightmare for anyone in a business meeting, but sometimes it can be worse than others.

For Federal Reserve Chair Janet Yellen, that moment came during her semi-annual testimony to the House Financial Services Committee on Wednesday.

When asked by Rep. Frank Guinta what the labor force participation rate (LFPR), the percentage of people with a job or actively seeking a job as part of the total population, Yellen seemed to be unable to draw the number from memory and had to shuffle through papers in order to find the number.

The LFPR is one of the most important numbers released monthly during the Bureau of Labor Statistics jobs report that the Federal Reserve uses to measure the strength of the US job market. Yellen herself has brought the number up in the past.

While the unemployment rate has declined under 5%, analysts have noted that the LFPR has plummeted after the financial crisis and that may be evidence that the labor market is not as strong as it appears.

It currently sits at 62.8%, by the way.

Check out the exchange: