Pending home sales for both single-family homes and condominiums went up for the 21st straight month in January compared with the year before, according to the Massachusetts Association of Realtors (MAR).

Pending sales figures (also called homes under agreement) are a leading indicator of actual housing sales in Massachusetts for the following two to three months.

"The spring home buying season came early for many buyers in January as the numbers showed they made offers and took advantage of market conditions instead of waiting," 2013 MAR President Kimberly Allard-Moccia, broker-owner of Century 21 Professionals in Braintree, said in a statement. "Late 2012 pending sales reports indicated that the closings for the first months of 2013 would most likely be up, but today’s report gives us reason to believe the same will be true about the early spring."

The number of single-family homes put under agreement in January was up 18.4 percent compared with the same time last year – 3,076 homes this year, versus 2,599 homes in January 201.2 The increase marked the 21st straight month of year-over-year increases. On a month-to-month basis, single-family homes put under agreement were essentially flat, compared with 3,062 homes put under agreement in December 2012.

The number of condos put under agreement in January was up 22.3 percent compared to January 2012 – 1,215 this year, versus 994 units in January 2012 – also the 21st straight month of year-over-year increases. On a month-to-month basis, condos put under agreement went up 13 percent from 1,076 units in December 2012.