The growth of pending home sales was sustained in March in most areas of the United States, according to the latest data from the National Association of Realtors.

The Pending Home Sales Index reached 110.5 during the month. This figure marked a 1.4 percent increase from both February and March 2015, each of which had a figure of 109. March was also the 19th consecutive month where pending home sales showed year-over-year growth, and its Pending Home Sales Index was the highest one since a figure of 111 recorded in May 2015.

The Pending Home Sales Index is a measure of transactions where a contract has been signed but a sale has not yet been finalized. The sale is typically closed within one or two months of the signing. The Pending Home Sales Index represents about 20 percent of existing home sales in the United States.

A figure of 100 indicates sales activity equal to the year 2001, when the National Association of Realtors began recording the data. In that year, existing home sales fell within the range of 5 million to 5.5 million, which is considered normal for the U.S. population.

Lawrence Yun, chief economist at the National Association of Realtors, says the continued growth of the Pending Home Sales Index indicates a strong start to the spring. This season tends to be a popular time for people to buy a home, since sellers often put their properties on the market at this time and it allows families to move after their children finish a school year.

"Despite supply deficiencies in plenty of areas, contract activity was fairly strong in a majority of markets in March," said Yun. "This spring's surprisingly low mortgage rates are easing some of the affordability pressures potential buyers are experiencing and are taking away some of the sting from home prices that are still rising too fast and above wage growth."

Yun said healthy employment levels and affordable borrowing costs may be spurring more people to buy a home. However, he said several areas are lagging in the construction of affordable single-family homes, especially in areas where strong job growth is producing more housing demand. If demand is strong and the inventory is tight, home prices may be too high for a household to consider purchasing a property.

The data suggests that affordability issues have started to hinder the housing market in the West, the only region which had a decrease in its Pending Home Sales Index. This figure was down to 95.3 in March, a 7.9 percent decrease from the previous year and a 1.8 percent drop from February. Yun said the median home price in this region has risen 38 percent in the past three years.

"As a result, pending sales in the region have now declined in four of the last five months and are lower than one year ago for the third month in a row," he said. "Closed sales in the region in March were also below last year's pace."

In the Northeast, the Pending Home Sales Index was up to 97, an 18.4 percent from March 2015. It was also 3.2 percent higher than February.

Pending sales in both the Midwest and the South were above 2001 levels, but exhibited slower growth. The figure in the Midwest was 112.8, up 0.2 percent from February and 4 percent from the previous year. In the South, the figure increased 3 percent from February and 0.6 percent from March 2015 to 125.4.