However, the ECB's financial support programme for eurozone banks has seen its balance sheet balloon since November to close to 30pc of its members' combined GDP.

Those 57 countries have a combined GDP (at Purchasing power parity; PPP) of USD7,740 billion.

The Commonwealth contains some of the fastest growing new economies in the world, with a combined GDP that has more than doubled in the last twenty years.

In 2011, its combined nominal GDP had grown to more than US$ 2 trillion.

And it's likely that the combined GDP of the four BRIC nations will exceed that of the US sometime before 2020.

It was reported that the combined GDP of all Arab Countries is less than that of Spain.

Its two major cities, Hartford and Springfield, have a combined GDP exceeding $100 billion per year, more than 16 U.S. States.

This is despite the Union's 54 countries having a combined GDP of more than £1.2 trillion.

Nursultan Nazarbayev, the Kazakhstan president, said "the union of three" will become "the most powerful" alliance, with "the combined GDP of the three countries approaching $2trn."

The EU can only spend a maximum of 1.2% of the combined GDP of all its Member States.