It was less than a basis point, but it was still an increase last month for the Monthly Treasury Average. The index has risen each of the last six months.
In January, the MTA was 0.17750 percent, according to an analysis of data from the Federal Reserve.
The index moved up from December 2012, when it was 0.17500 percent. It has increased each month since July, when it stood at 0.14750 percent, and hasn’t fallen since April, when it came in at 0.14667 percent.
MTA was also higher than in January 2012, when it worked out to 0.16917 percent.
The index is determined from an average for each of the last 12 months of the daily average for the yield on the one-year Treasury note. The daily average was 0.15 percent in January, down from 0.16 percent as of December and up from 0.12 percent in January 2012.
A much more widely used index for adjustable-rate mortgages is the yield on the one-year Treasury, itself, which slipped to 0.15 percent at the end of January from 0.16 percent at the end of December.
ARM share rose to 4.8 percent in the U.S. Mortgage Market Index report from Optimal Blue and Mortgage Daily for the week ended Feb. 1 from 3.2 percent seven days prior.