How often does NADA update its used auto value guides?

the National Automobile Dealers Association (NADA) updates its used auto guide values monthly for retail, loan and trade-in values and weekly for auction values. Customers can use this guide to determine the worth of a used vehicle before purchasing or selling it.

NADA was founded in 1917 and is based in McLean, Virginia. The organization represents more than 19,700 vehicle dealers. In 1998, it started publishing its guide service online. NADAguides is designed to assist customers by providing accurate information on new and used cars. Those interested in used cars can find the most updated information from NADA using its Official Used Car Guide, which is offered online as NADA Values.