Whether it’s planning infrastructure expansion or hiring more public safety officers, growing cities face numerous challenges as they adapt to accommodate more residents. When these decisions multiply and become more complex, many localities opt to change their form of government.

Smaller cities – typically between 5,000 and 50,000 residents – are most likely to consider altering their governing structure as they expand. Most often, these municipalities abandon mayor-council governments for council-manager arrangements.

Updated figures from the International City/County Management Association highlight this trend, with council-manager governments now accounting for 48.6 percent of all municipalities with populations of at least 2,500. That’s up from 36.5 percent of governments 20 years ago.

Cities without managers typically consider new governing structures upon reaching populations around 5,000, according to James Svara, director of the Center for Urban Innovation at Arizona State University. "It’s natural for the cities that are small to reexamine themselves and make a change," he said.

In 1990, there were 5,475 Census-designated places exceeding the 5,000-resident threshold. By 2010, this number had grown to 6,445.

With more resources, larger governments have funds needed to hire city managers. Svara, who has studied government forms extensively, said they also tend to take a more organized approach to government.

"As they get larger, the government needs to do more, perform at higher levels, and they recognize this is beyond the capabilities of elected officials,” he said.

As of 2011, council-manager forms made up 38 percent of all municipalities with populations between 2,500 and less than 5,000. This figure jumps to 47 percent of governments with populations between 5,000 and 9,999, and 53 percent for those with at least 10,000 residents and fewer than 25,000, according to ICMA’s Municipal Yearbook.

Mayor-council structures account most of the remaining governments. A much smaller portion – less than 10 percent – consists of either commissions or town meetings.

The rise of the council-manager form accelerated after World War II, primarily in sprawling suburban areas, according to Svara.

Along with cities experiencing recent population upswings, newly-incorporated municipalities also account for some of the added government counts.

The following chart illustrates historical ICMA data measuring government types:

Michele Frisby, ICMA’s public information director, said part of the shift could be related to the association’s data collection process, since they now work to confirm information with respondents unsure of their government classification type.

In recent years, the ratio of council-manager to mayor-council governments has remained relatively stable. This may be due, in part, because many of the nation’s largest cities have switched from council-manager to mayor-council governments.

ICMA’s numbers indicate mayor-council structures account for the bulk of city governments serving populations exceeding 250,000.

While referenda aren’t common, they’re much more likely to occur in more populous areas, driven in large part by the political dynamics of cities, Svara said.

In Sacramento, Calif., the city council voted last week to approve a ballot measure that, if passed in November, would create a commission to examine the city's charter. Mayor Kevin Johnson had pushed for a strong-mayor ballot initiative earlier this year, but those plans failed to gain enough public support.

Other cities are fine-tuning existing governing structures instead of swapping them out with new ones.

Svara said some mayor-council cities are employing more chief administrative officers and managers. At the same time, council-manager governments have recognized the need for strong political leadership.