According to the August Trulia Rent Monitor, rental rates in the country's largest metro markets hiked, but the rate of increase has slowed slightly compared to the year-over-year rate in May.

Rental rates rose 4.7 percent in August compared to the year before, but the rates have slowed considerably compared to the 5.8 percent annual bump recorded in May.

In individual metros, Houston and Seattle experienced yearly jumps of more than 10 percent, while increases in metro areas Denver, San Francisco, Miami, Oakland and Boston slowed slightly over the May report.

The slowing of rental rates corresponds with a slowing of apartment market REITs, which recorded a steady but slowing growth according to Real Estate Weekly.

Both of these factors show that although the apartment market is still strong, it is beginning to slow slightly due in part to increased construction bringing an onslaught of new units onto the market.

Rental property management officials concerned with the slowing market could consider revamping marketing efforts by making use of community websites and craiglslist rental postings to advertise new properties available for rent.