Luxury motors on the streets of West London, now the EU's richest area | Daniel Leal-Olivas/AFP via Getty Images West London EU’s richest region, Brussels out of top 3 Eurostat’s ranking is based on gross domestic product per capita.

The central Brussels region has been downgraded on a list of the EU’s richest areas, according to data published Thursday.

The ranking by Eurostat, the Commission's statistics agency, is based on gross domestic product per capita in 2015, expressed in terms of purchasing power.

Brussels is now placed fourth, down from third in 2014, behind the Inner London West region, Luxembourg and Hamburg. Bratislava rounds out the top five.

The GDP in the Belgian capital, which is home to many of the EU institutions, was at 205 percent of the EU average in 2015. London, at 580 percent of the average, was far ahead of Luxembourg (264 percent) and Hamburg (206 percent).

Twenty of the EU's 276 regions recorded a GDP that was 50 percent higher than the EU average. Most of these were in Germany, the U.K., Austria and the Netherlands.

Severozapaden in Bulgaria (29 percent of the GDP average) was lowest on the list. Mayotte in France (32 percent), Severen Tsentralen and Yuzhen Tsentralen in Bulgaria (both 33 percent) and Nord-Est in Romania (34 percent), were also near the bottom of the list.