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New York (CNN Business)Since its founding in 1913, the US Federal Reserve has fought to achieve three goals: maximum employment, stable prices and moderate long-term interest rates. But that's about all that's remained consistent in the central bank's 109-year legacy of monetary policy.

Economists at the Fed work hard to maintain the institution's reputation as a stoic pillar of economic wisdom — unperturbed by politics or the whims of the day, all-knowing and, most importantly, effective. This image obsession serves an important purpose: The central bank's dependability hinges on Americans believing that it's ... dependable.

That's no secret. In their June meeting minutes, officials noted strong credibility and communication had "been helpful in shifting market expectations of future policy and had already contributed to a notable tightening of financial conditions that would likely help reduce inflation pressures by restraining aggregate demand."