$15 trillion Global Infrastructure spending gap over the next 22 years

Nearly a fifth of the $94 trillion in global infrastructure investment needed by 2040 risks being unfunded if current spending trends continue according to the G20-backed Global Infrastructure Hub. To close the spending gap, annual infrastructure spending needs to rise to 3.5 percent from 3 percent of global gross domestic product.

The GIH, set up by the G20 in 2014, aims to help to increase opportunities for public and private investment in infrastructure around the world. It is funded by governments including Britain, Australia, China, Korea and Singapore.

Every year, $3.7 trillion needs to be invested in infrastructure to meet demand - equivalent to the annual economic output of Germany, the world's fourth largest economy.

And to meet United Nations Sustainable Development Goals, which aim to ensure universal access to drinking water and electricity by 2030, investment needs to increase to 3.7 percent of global GDP between now and 2030, it said.

The investment is needed to support global economic growth and fill gaps in infrastructure in both developed and developing countries, the GIH said.

The United States will have the largest gap in infrastructure spending, at $3.8 trillion, while China will have the greatest demand, at $28 trillion, representing 30 percent of global infrastructure investment needs.

Underpinning the need for increased spend is an expected rise in the global population by 2 billion people by 2040 and 46 percent increase in the urban population, driven by Asia, which needs $52 trillion in investment by 2040 to meet that demand.