The Fed's dual mandate — delivering both maximum employment and low inflation — requires a balancing act: Low interest rates help to bring down unemployment, but according to economic theory, they also risk causing inflation. In reality, thanks largely to China, inflation has not been a problem for decades.
The big picture: The Fed's preferred inflation measure, PCE, has been below 3% for more than 25 years. Unemployment, on the other hand, has been a tougher problem to solve: It reached 10% in late 2009. The temptation, then, is always to keep interest rates very low, as President Trump desires.