When it comes to thinking about the Federal Reserve and banks, some investors might not be looking at the right part of the market. On Friday morning, the Fed said it wouldn't extend an emergency pandemic rule exempting Treasurys and reserves from a big-bank leverage measure beyond March 31, when it is due to expire. Without that exemption, big banks will be running closer to maximum leverage levels. One worry has been that this could force some balance-sheet shrinking and selling of longer-term Treasury bonds, putting further upward pressure on those rates.