Luxury housing prices across the globe logged weak growth in the second quarter of 2018 as the introduction of new property market regulations, the rising costs of financing and political uncertainty resulted in more moderate price growth across international top markets, according to Knight Frank’s prime global cities index.

Prices have gone up at their slowest rate since 2012—logging just 2.6% increases overall. The poor performance is not due to more cities registering annual declines, Thursday’s report said, but instead, is caused by prices in the top-performing cities rising more slowly.

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The report tracks quarterly growth in prime properties—or the top 5% of the housing market—in 43 major cities.

Last quarter, seven cities registered double-digit annual price growth, but this quarter only three—Guangzhou (11.9%), Singapore (11.5%) and Madrid (10.3%)—saw growth of 10% or more.  The margin, meanwhile, between the strongest and weakest performing city shrunk from 33% to 20%, said Kate Everett-Allen, partner of international residential research at Knight Frank, in the report.

In the U.S., San Francisco (9.5%) and Los Angeles (7.8%) were the best performers, as a strong economy and buoyant labor market has boosted housing demand. New York, meanwhile, ranked 31st, logging minimal annual price increases of just 0.1%.

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In London, where the prime market has been hindered of late by increases in property tax for high-end and second-home buyers, as well as Brexit uncertainty, prices fell 1.8%.  

But Stockholm ranked lowest on the list, as prices fell 8.4%.