The Federal Reserve balance sheet

Total assets held by the Federal Reserve, from the weekly H.4.1 release. The balance sheet grew through two rounds of large-scale asset purchases and has been shrinking since the Committee began allowing securities to mature without reinvestment.

The decline is passive. Securities roll off as they mature, up to a monthly cap; nothing is being sold. When less than the cap matures in a given month, the reduction is smaller — which is why the line falls in uneven steps rather than a straight slope.