Over two billion people live in countries with unaffordable internet, many of them in Africa, which is resulting in a slowdown in adoption rates.

That is according to the fifth annual Affordability Report released by the Alliance for Affordable Internet (A4AI), which finds that as little as 1GB of mobile data is too expensive for billions people across the world, with African countries especially expensive.

This is a situation that has barely improved over the last year, with progress on the policy front painfully slow, meaning more than 2.3 billion still cannot afford 1GB of data.

As a result, there has been a serious slowdown in the rate at which people are coming online. Last year's report predicted that global internet penetration would hit 50 per cent by the end of 2017, but a downturn in the growth of internet access and use means A4AI has now revised the date for this to mid-2019.

"Inability to afford a basic internet connection remains one of the most significant - and solvable - barriers to access," the report said.

"This issue is particularly acute in low- and middle-income countries, where 1GB of data costs over five per cent of what people earn in a month - a price that is well over the affordable threshold of 1GB of data priced at two per cent or less of average income."

The report lays the blame for this on the fact that policy progress is slowing, with not enough governments adopting mechanisms such as universal service funds (USFs) to ensure more people can afford internet connectivity more quickly.

"Despite increasing recognition of the critical relationship between online access and economic growth, the pace of policy change to drive internet prices down marked its slowest improvement to date, with policy scores increasing by just one per cent since last year," said the report.

In all, over 60% of countries have unaffordable internet. Of the 61 countries studied, just 24 had affordable internet, with seven of these African: Mauritius, Morocco, Nigeria, South Africa, Ghana, Botswana and Tunisia.

"While we have seen a few bright spots of the policy leadership needed to advance affordable internet access, we are deeply concerned to see that policy progress has largely stagnated. Failure to prioritise needed broadband policy reforms has left billions of people offline, and has contributed to a significant slowing in the rate of people coming online," said A4AI executive director Sonia Jorge.

"Every moment that these billions are unable to participate in digital development is a lost opportunity for economic, social, and political growth. Policymakers, the private sector, and civil society must come together to take immediate action to develop and implement the policies needed to connect everyone and accelerate internet growth."