UK surplus? U.S. surplus? Who knows, trade statisticians say

The 33 billion-pound mismatch for 2016 was derived from British statistics showing the country had a trade surplus in services with the United States of 23 billion pounds while the United States reported a services surplus with Britain of around 10 billion pounds.

Britain's Office for National Statistics said it and the U.S. Bureau of Economic Analysis had found the causes behind only 4 billion pounds ($5.6 billion) of this mismatch in services trade between the two countries.

"As the UK prepares to leave the European Union and seeks to negotiate its own trade deals, it has become even more crucial that we have a deeper understanding of our trading relationship with other countries," ONS statistician Adrian Chesson said.

Britain's government has said it wants to ensure its services firms, ranging from banks to universities, can continue to do business easily in the EU after Brexit and can expand in new markets further afield once Britain leaves the bloc.

The 4 billion-pound difference so far explained by the ONS and the BEA was primarily due to different methodologies for measuring financial services, the ONS said.

Furthermore, the United States included British crown dependencies, such as the Channel Islands, in its definition of the United Kingdom in its figures, but the ONS excluded them from its figures.

"However, there is still a sizable gap between the two sets of figures that we haven't yet explained. It may be that different data sources and sampling variability could explain some of the differences," Chesson said.

The ONS said the problem of trade asymmetries was not limited to Britain and the United States - adding up the globe’s trade statistics, it found that the world has a trade surplus with itself of around 350 billion pounds.

($1 = 0.7107 pounds)

(Writing by William Schomberg. Editing by Jane Merriman)