New York was named the world's top financial center in Z/Yen's annual index, overtaking London as companies become increasingly concerned by the prospect of the U.K. losing access to the EU's single market.

The big picture: The Global Financial Centres Index ranks cities based on factors grouped into five broad categories: business environment, human capital, infrastructure, financial sector development and reputation. Uncertainty surrounding Brexit negotiations has prompted financial services firms, which account for 12% of the U.K.'s GDP, to consider moving their operations out of London — providing a boost to other cities in Western Europe and Asia.

Top 10 global financial hubs: