I am replying because I asked the exact same question in my macroeconomics class in business school. If the economy expands faster than population growth, that implies economic output per person is increasing, which means higher productivity, which means personal incomes are increasing.
The article you cite is a little misleading in that the Fed’s actions were not directly aimed at increasing economic output but rather to help ensure the financial system continues running by providing cash so obligations can be met.
However, this is a short term fix, as when the Fed does this, it increases the money supply; if this increase in the money supply is not reversed it results in inflation. More money correlated to the same economic output as before = inflation. Some argue that loose money got us into this mess in the first place.
The Fed cannot directly control the economy – that is, people still go to work and do the same jobs, whatever the Fed’s actions – but its influence on the money supply can affect the economy. Cynics would say, apparently only negatively.
