The tax adjustments are part of a broader strategy by cities to aid homeowners — who continue to struggle financially since the home mortgage crisis. In Richmond, Calif., lawmakers are attempting to use eminent domain to seize underwater mortgages to try to help homeowners keep their houses.

Housing experts say the arrival of newcomers to formerly working-class areas — from the Mission District in San Francisco to the Shaw neighborhood in Washington — is distinct from previous influxes over the past 30 years because new residents are now far more likely to choose to move into new condominiums or lofts instead of into existing housing, making the changes more disruptive.

“This latest wave of gentrification has happened very quickly, and cities are cognizant to keep from turning over entirely,” said Lisa Sturtevant, executive director of the Center for Housing Policy, a nonprofit research group. “And cities where property values are up and budgets are generally more stable have the wherewithal to provide tax breaks.”

Ms. Sturtevant said that given that many of the younger, newer arrivals do not necessarily plan to stay for long, cities are making a sensible economic choice.

“There’s less personal investment and less incentive to stay, so cities are saying, ‘Let’s invest in the stayers,’ ” she said.

In Boston, which an analysis by the Federal Reserve Bank of Cleveland last year found had the highest gentrifying pressure in the nation — followed by Seattle, New York, San Francisco, Washington and Atlanta — concluded that about one-fourth the city’s population lived in gentrifying neighborhoods.

“Property values are increasing exponentially, and longtime homeowners are victims of the success story,” said Stephen J. Murphy, a city councilor in Boston who co-introduced legislation allowing residents who have owned homes for more than 10 years and whose property taxes have increased by 10 percent or more to defer property tax payments until they sell their home. The bill, approved by the City Council, is pending the approval of the state legislature.