Colorado's six major metropolitan areas saw a 4.9% drop in apartment vacancies when comparing the second quarter of 2012 to last year, the Colorado Division of Housing said.

The rise in rentals is the natural outcome of forming households choosing the rental option, the division concluded in its new report. 

The report incorporates apartment rental data from the metro areas of Colorado Springs, Denver, Ft. Collins, Grand Junction, Greeley and Pueblo.

Today's rental vacancy rate in those areas is down from 5.2% a year earlier and the lowest vacancy rate on record since the first quarter of 2001, the division of housing said.

All of the state's metro areas saw a notable uptick in rental demand. In just the Denver metro area, the rental vacancy rate remained unchanged at 4.8%. The Fort Collins/Loveland metro area saw its own vacancy rate fall to a new record rate of 3.5%.

"In spite of some relatively weak job growth in some metros, household formation continues in Colorado, and people are looking to rent apartments," said Ron Throupe, a professor of real estate at the University of Denver’s Burns School of Real Estate and Construction Management and author of the report. "In those areas with the most job growth, like Larimer county, the apartment market has become very tight."

The state's average rent also increased on limited supply, rising to $942 in 2Q. That compares to an average rent of $877 a year earlier.