The US economy grew at its strongest rate since 2014 in the three months to September, increasing speculation that the Federal Reserve will raise interest rates before the end of the year.

The world’s largest economy grew at an annual rate of 2.9 percent in the third quarter, the Commerce Department said on Friday. This is above analysts’ expectations of 2.5 percent, and far higher than the 1.4 percent growth seen in the previous quarter.

Consumer spending was the main driver of the economy over the last three months, increasing at a rate of 2.1 percent. This was, however, a slowdown from the 4.3 percent rate seen in the second quarter.

The stronger-than-expected figures are likely to increase speculation that the Federal Reserve will raise interest rates before the end of the year. Janet Yellen indicated at the Fed’s last major meeting that, dependant on upcoming figures, December may be the time to make a move.

Investment in mining, exploration, shafts and wells fell by 31.5 percent, with investment in residential construction also taking a hit for the second quarter in a row.

Exports increased at their fastest rate since the fourth quarter of 2013, growing by 10 percent.