The rental market continues to to show its strength, CNBC reports, with the fourth and final quarter of 2011 marked by the lowest national vacancy rate of the year at 5.2 percent.

That represents a low not reached since 2001 despite a seasonal trend of higher vacancies in winter during previous years. According to real estate data firm Reis, the fourth quarter of the year is also typically low in leasing activity. This time, on the other hand, the sector performed well in almost every area tracked by the firm.

According to Reis, asking and effective rents were a slight disappointment because they only increased by 0.4 and 0.5 percent, respectively, coming in below projections. It remains worth noting, however, that even a small increase represents continuing momentum for the multifamily sector, which was relatively strong throughout 2011.

Analysts attributed the drop in performance to weak economic growth and employment, which have typically been limiting factors on apartment rental business in the past. According to the news source, experts have said that high-quality properties experienced much stronger rent increases, as high as 5 or even 10 percent, while the national average was weighted down by lower-quality units.

Rental property management firms and apartment industry stakeholders may benefit from further growth in the near future, if current projections are fulfilled.