When the prime rate decreases, your variable APR will decrease by the same amount. But when the prime rate increases, your variable APR will also increase by the same amount.
The lending bank profits from the premium you pay over the prime rate. Generally, this premium doesn't decrease as long as you hold the card, although some banks will lower your interest rate if you have a long history with them, your account is in good standing, and you ask them nicely over the phone.
https://en.wikipedia.org/wiki/Prime_rate
When the prime rate decreases, your variable APR will decrease by the same amount. But when the prime rate increases, your variable APR will also increase by the same amount.
The lending bank profits from the premium you pay over the prime rate. Generally, this premium doesn't decrease as long as you hold the card, although some banks will lower your interest rate if you have a long history with them, your account is in good standing, and you ask them nicely over the phone.