The year 2012 is on its way to becoming the most affordable year housing has seen since recordkeeping began in 1970, according to data from the National Association of Realtors (NAR).

In November, the NAR’s Housing Affordability Index reached 198.2, down 2.5 index points from October, but up 1.5 points from a year ago.

The index determines affordability based on the relationship between median home price, median family income, and average mortgage interest rate. The index also assumes 25 percent of gross income is devoted to principal and interest and a 20 percent down payment would be made.

Based on data up to November, NAR also projects the index will set a record high of 194 in 2012, beating the high of 186 in 2011.

However, record affordability doesn’t necessarily translate into more homeowners.

“Although 2012 was highest on record, the excessively tight underwriting precluded many would-be homebuyers from locking-in generational low interest rates,” explained Lawrence Yun, NAR chief economist.

NAR president Gary Thomas, added, “A more sensible lending environment that makes it easier for other financially qualified buyers to get a mortgage would allow many more households to enter the market, boosting home sales as much as 10 to 15 percent.”

While affordability is expected to see a new high in 2012, NAR expects affordability in 2013 to drop to 160. NAR noted an average of 160 means a median-income family would have 160 percent of income necessary to buy a median-priced existing single-family home.

“Rising home prices and a gradual uptrend in mortgage interest rates will offset improvements in family income, but 2013 likely will be the third best on record in terms of household buying power,” Yun noted.