The job of Federal Reserve Chair has become more important since Congress has become more dysfunctional. In an ideal world, the government has a mix of fiscal and monetary tools to use to help to smooth out the inevitable bubble and busts of an economy. Now we really have just monetary policy, the tool of the Fed. In the recovery from the Great Recession, when unemployment was still above 8%, the media and Republicans made a great deal of noise about deficits. Now that unemployment is only 4.1%, the Republicans have decided to add another trillion to the debt this year with no noise from Republicans (they're the ones creating this) and very little noise from the media. This is backwards and the Fed has had to work against Congress in their efforts to keep the economy from extremes during the recovery. Yellen has done that flawlessly.
For 100 years we had Fed Chairmen. Then, four years ago, Obama appointed Janet Yellen to succeed Ben Bernanke as Fed Chair. Here is how the economy has performed during her four-year term.
The uninterrupted streak - a new record
When Yellen took over as Fed Chair, the American economy had been creating jobs every month for 40 months. That's great but on two different occasions, the streak had lasted longer: 46 months in the mid-2000s and 48 months in the late 1980s. 
Not once did the jobs report come in negative during her time as Fed Chair. The streak is now 88 months and counting; she set a new record each month for the last 40 months of her tenure, shattering the old record and bringing the unemployment rate down from 6.7% to 4.1%. No other Fed Chair presided over a time in which every single monthly jobs reports was positive.Second best annual job growth
Uninterrupted job creation makes it easier to create a lot of jobs. During her four years the economy did. Only one Fed Chair - Miller who served for only 17 months during the 1970s - presided over a higher annual average job growth. (And wasn't it curious how the media continued to whine about so-so job creation rates, as if they had any instances of it being better during a four year or longer Fed term?)
Second best annual rate of stock market return
The market returns during her tenure were also second to only one other Fed Chair - Volcker. It seems fitting that the market began falling spectacularly after her last meeting Wednesday and before Powell's first day of work Monday. (Speaking of which, Powell did have a miserable start in his first two days. After Monday's huge sell off, the market return for his first day worked out to a 99.9% annual return which would have made him the first Fed Chair to have lost the entire stock market in his first year on the job. "Where are the returns Jerome?" "I don't know. Yellen seems to have taken them when she cleared out her desk.")
Lowest Inflation
The Federal Reserve has two goals: keep unemployment and inflation low. No one presided over lower inflation rates than Yellen. The goal is 2%. Her highest year was 2.1%. Only Bernanke - who was dealing with horrendous unemployment rates - was close to her and most Chairs were more than double that.
Trump, unsurprisingly, decided that Yellen's performance wasn't good enough to warrant a second term and thus hers will be the shortest term of any Fed Chair since 1979 when Carter decided that inflation was too high and he needed to truncate G. William Miller's term and replace him with Volcker.*
Of course it was unsurprising that Trump would replace Yellen. In Trump's final campaign ad, he lumped Yellen with Clinton, Soros and other world leaders as "globalist" financiers "who don't have your good in mind."
As it turns out, for a woman who didn't have our good in mind, she did pretty good. I'd go so far as to say that her performance was flawless. Let's hope it's not another century before a president has the good sense to appoint the second woman to head the Fed.
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*(It's worth noting that when Carter interviewed Volcker for the job as Fed Chair, Volcker warned him that his approach to squeezing out inflation would hurt the economy short-term and about the time Carter was running for reelection the economy would be in bad shape. Carter said, But this is what we need to do. And sure enough, in November of 1980 when Americans elected Ronald Reagan to take Carter's place, unemployment was at 7.5% and continuing to rise.)
