The Fed stopped Quantitative Easing a while ago, and the value of its balance sheet fluctuates around the $4 trillion level. As their holdings mature, their aggressive position in the bond market will slowly unwind. Or will it? The Fed is likely to decide to re-invest proceeds in more bonds and obligations, replacing the matured debt with new ones, but not adding to their overall position unless there is a crisis again. Until their first moves where they doubled their balance sheet quickly, from $800 billion to $1.6 trillion, this measure of the money supply moved steadily at about a 6% annual rate, sometimes a little more, sometimes a little less, about half equal to economic growth and the other half to inflation. Whether or not the Fed will reduce its balance sheet or not is still a question in my mind. They could just hold steady, and let inflation and growth catch up to them, which will take quite some time, but not scare the markets. But something always happens that's not according to plan, and the Fed will be interesting to watch as they move from this unchartered territory to another.