Shoppers have another option when trying to nail down the best rate for a new car as well as gauge their new vehicle's affordability based on income.

The initial release of the monthly U.S. Auto Buyer’s Affordability Index (ABAI) from Requisite Press LLC gives shoppers and dealers a point of reference when researching new-car gauging affordability.  

The new index employs the 20-4-10 auto financing rule, which consists of a minimum 20 percent down payment, a maximum four-year loan term, and monthly payments of no more than 10 percent of gross household income.

“The rule is widely recommended by personal finance experts to maintain financial security, avoid excessive interest costs, and preserve future investment opportunities,” company officials shared.

The new index is designed to provide “regular, ongoing consumer awareness of new-car affordability considerations for improved household financial health,” the company shared.

The company also offered a bit of explanation regarding the past month's index scores.

For April, the ABAI index sits at 52.1, on a scale of 0 to 100.

Explaining the meaning behind the scores, company officials said, “A score of 52.1 indicates that a U.S. median-income buyer following the 20-4-10 auto financing rule can only afford 52.1 percent of the April 2014 new-car average transaction price."

April's number equates to a maximum affordable price of $15,795, assuming a median income of $53,043 and an average transaction price of $30,339.

The company explained with high loan amounts and longer loan durations, affordability information such as the new index is becoming more and more important to consumers.

“The monthly ABAI was developed to enable buyers to easily view current new-car prices in the context of sound financial advice,” the company said.