ARM index values are pulled every 4 hours from the following sites.
1 Year LIBOR: https://www.wsj.com/market-data/bonds
1, 3, 5, 10 Year Treasury (CMT): https://www.wsj.com/market-data/bonds/keyinterestrates
11th District Cost of Funds (COFI): https://www.bankrate.com/rates/interest-rates/11th-district-cost-of-funds/
Prime Rate: https://www.wsj.com/market-data/bonds/moneyrates
*Note: Optimal Blue does not store the ARM index from the day of lock. The ARM index on locked loans will update as the values from these sites change.