Although pending sales in the United States remained at high levels in March, they slowed down slightly from the previous month.

The National Association of Realtors' Pending Home Sales Index for the month stood at 111.4. This was down from 0.8 percent from February's figure of 112.3, but it was still 0.8 percent higher than a year ago.

The Pending Home Sales Index is a measure of sales activity where a contract has been signed but the transaction has not been finalized. Once the contract is signed, the sale is usually closed within two months. For this reason, the index provides a good indicator of anticipated short-term existing sales activity.

An index of 100 is equal to the average activity in 2001. Between 5 million and 5.5 million homes were sold in that year, and this sales activity is considered normal for the current U.S. population.

"Home shoppers are coming out in droves this spring and competing with each other for the meager amount of listings in the affordable price range," said Lawrence Yun, chief economist at the National Association of Realtors. "In most areas, the lower the price of a home for sale, the more competition there is for it. That's the reason why first-time buyers have yet to make up a larger share of the market this year, despite there being more sales overall."

In its latest report on existing home sales, the National Association of Realtors noted that there has been a year-over-year reduction in housing inventory for 22 straight months. Yun said a lack of available homes for sale helps spur competition and higher prices, which may drive away some buyers.

However, other buyers have shown a willingness to engage in bidding wars for available properties. The Realtors Confidence Index for March found that 42 percent of home sales during the month were at or above listing price, the highest level since the National Association of Realtors began tracking this information in December 2012.

"Sellers are in the driver's seat this spring as the intense competition for the few homes for sale is forcing many buyers to be aggressive in their offers," said Yun. "Buyers are showing resiliency given the challenging conditions. However, at some point—and the sooner the better—price growth must ease to a healthier rate. Otherwise sales could slow if affordability conditions worsen."

Yun anticipates that there will be about 5.64 million existing home sales this year, a 3.5 percent increase from the 2016 total of 5.45 million. He also expects median existing home prices to increase 5 percent from the previous year. Both increases would be down slightly from 2016, when existing sales rose by 3.8 percent and median prices were up by 5.1 percent.

Pending sales were down from the previous month in all regions except the South. There, the Pending Home Sales Index was up 1.2 percent from February and 3.9 percent from March 2016 to stand at 129.4.

In the Northeast, the index fell 2.9 percent to 99.1. However, it was still 1.8 percent above the previous year.

Pending sales in the Midwest fell 1.2 percent from the previous month and 2.4 percent from the previous year, with the region's index coming to 109.6 in March. The Pending Home Sales Index in the West was 94.5, a decrease of 2.9 percent from February and 2.7 percent from March 2016.