A 2% wealth tax proposal was one of the highlights of Brazil's presidency of the G20, which preceded the passing of the baton to South Africa. The jury is out on whether the tax is implementable as some countries, such as the US, are not on board despite being part of the group, which represents between 70% and 85% of global output. The tax could impact about 3,000 dollar billionaires across the world. 

The tax would raise an extra $250bn (R4.5-trillion) per year, which could be used to address issues such as climate change or global poverty. The apparent snag is its feasibility. Unimplementable decisions — as good as they sound — risk turning the G20 into just a talkshop instead of a body that pulls together the most consequential presidents and their governments. A G20 unifying agenda is impossible due to fragmentation, insular countries and their interests...