8. Janet Yellen

Title: Chair of the Board of Governors of the Federal Reserve

Country: US

Age: 69

As the head of the Federal Reserve — the first woman to hold the job — Janet Yellen is the guardian of the US economy. The results have been good so far: The US is closing out the year with a period of growth, adding 271,000 jobs in October and lowering unemployment to 5%, according to the latest jobs report. The strong economic performance has many speculating that an interest rate hike from the Fed is imminent. It would be the first in almost a decade.

It's a hefty decision with profound economic implications, and investors and company executives worldwide parse Yellen's every word for hints to her plans. A small rate hike would indicate the economy is thriving and strong, but some worry that lifting rates too early will damage individuals' spending ability and hamper growth. But too much growth and improvement in the labor market without a rate hike could lead to inflation. Either way, Yellen holds a position of immense power, and her decision will affect the entire country.