In the US, Prime is affected by the Federal Reserve lending rate to banks; historically, Prime is about 3 percent above the Fed rate.
The Federal Reserve loans to Bank A at 1%
Bank A loans to Bank B at 4%
Both banks – A & B – will recalculate variable-rate loans like ARMs on that 4% Prime figure.
ARM rates are frequently defined as “% above Prime” – that gap is usually called the “margin” or “spread.” Just remember those 3 layers in Prime: Federal Reserve Bank A Bank B And finally, YOUR rate.