Steffan Ball was appointed earlier this month, and began work at the Treasury last Monday, the government confirmed today.
Ball previously worked as an economist for four years at Citadel, which manages $27bn (£21bn) for clients.
Before that he was an economist at the US Federal Reserve from September 2008 until December 2013.
Ball's areas of study at the US central bank included the American housing market, consumer spending, as well as models for consumption forecasts.
He also helped in writing speeches for Fed governors, and briefing former Fed chair Ben Bernanke. Bernanke later joined Ball at Citadel.
During his time at the Fed Ball worked on a three-month secondment to the Bank of England, where he worked at the Macro Financial Analysis Division. According to his profile on the Linkedin social network he "analysed the effects of quantitative easing on GDP and developed models to forecast UK consumer spending".
His appointment was first reported by Reuters.
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