Researchers at the University of California, Santa Barbara, the University of Georgia and the Sea Education Association pieced together production, use and disposal data for every type of plastic made between 1950 and 2015.
They found that 8.3 billion tonnes of virgin plastic had been produced. Of the 6.3 billion tonnes that had already become waste, only 9% was recycled, 12% was incinerated and 79% ended up in landfill or loose in the environment.
This is the paper behind the famous '9% recycled' figure. It matters because it showed that the plastic problem is mostly a disposal problem: nearly four-fifths of everything we have made is still sitting somewhere on the planet.
It is sometimes quoted as a current annual recycling rate. It is not: the 9% is a cumulative share to 2015. The Organisation for Economic Co-operation and Development (OECD) separately puts the annual rate for 2019 at 9% too, which is why the two are often confused.