A crucial barometer of global banking health is losing its clout as a macroeconomic indicator, but the move is benefiting some consumers and others whose low interest-rate loans still are pegged to it.

Known as the London interbank offered rate, or Libor, the barometer helps price trillions of dollars of derivatives and home and corporate loans. Calculated daily, Libor is supposed to measure borrowing costs for a panel of banks globally. The rate "floats," or ebbs and flows depending on how much banks charge one another.