WASHINGTON, DC—If there has been one sector that has fueled the local commercial real estate market over the last few years, it has been multifamily. Apartment investment sales and fundamentals have remained solid even as the office sector faltered. Needless to say, the construction pipeline has been robust for apartments.

So it is no small matter when the market signals that a shift may be underway, which it did at the end of the fourth quarter, according to DTZ's stats on the local markets. The good news from its report: the District of Columbia posted positive absorption during the quarter. The bad news: the District was the only area to post positive absorption.

In Northern Virginia, demand fell behind supply during the fourth quarter; 923 units delivered and absorption registered a negative 515 units with only two out of eight submarkets posting positive absorption, according to DTZ. The situation in Suburban Maryland was much the same, the report also noted. Demand was a negative 318 units.

This is not to say the news is all bad; both Virginia and Maryland posted positive absorption for the year.

Also, investment sales continue to fuel activity here. Multifamily investment sales volume registered $3.3 billion during 2014, a continuation of a steady upward trend in which sales are now double what it was only four years ago.

Still absorption stats will be watched closely for the first quarter.

And even if the trends that appeared in the fourth quarter continue in the first, there is reason to remain optimistic about the sector's long-term prospects.

DTZ notes that there are 18,000 units under construction across the DC area, so region will likely continue to see vacancy increase in the short-term. However, long-term population and job growth forecasts suggest there will be a pronounced shift in the amount of multifamily product that will be needed on an annual basis, it concluded.

Indeed, it called the uptick in annual supply part of the "new normal" for the DC area "in terms of what is needed to accommodate the expected increase in annual demand for the foreseeable future."