The Harris County Budget Department released its annual population report in late February showing continued growth in the county, particularly in unincorporated areas.

According to the report, if the unincorporated areas of Harris County—which includes Spring, Klein and parts of Cy-Fair—was a city, it would be the second-largest in Texas and the fifth-largest in the U.S. The unincorporated area of the county is more populous than 14 U.S. states, according to the report.

As of Dec. 31, 2016, the population of Harris County was estimated at 4.7 million residents, according to the report, which draws from U.S. Census Bureau estimates, Harris County Appraisal District data and historical trends. The county population has grown by about 100,000 each year since 2010.

A unique feature of the area is that over 80 percent of the county’s growth since 2001 has taken place in the unincorporated areas of the county, which now represent 43 percent of the county population.

Based on the current trends, the county population will exceed 5 million in 2020 and could reach 5.6 million by 2025, according to the report. If the current trends continue, the unincorporated population will surpass that of the city of Houston in 2020 and grow to 2.8 million by 2025.

"There are some who would say the unincorporated [parts of the county are already] larger than the city," Harris County Precinct 4 Commissioner Jack Cagle said. "The trend is continued growth, and therefore we are diligently studying our maps and trying to find partners to stay on top of rendering the services people are coming to expect."

The report concludes that uncontrolled growth in unincorporated Harris County will represent increased challenges for county government.

"[County residents] expect the same services they would get from the city," Cagle said. "That's very difficult to achieve when you don't have the same source of funding."