Trade taxes refer to taxes levied at the border. These are mainly import tariffs and export duties, although export duties have almost entirely disappeared. Figure 14 shows that, when countries are weighted by the size of their economy, trade tax revenues have declined by a third as a share of GDP. The decline has taken place in upper middle income and lower middle income countries, while trade tax revenue in low income countries has remained stable as a share of GDP.

Exceptions include Botswana, the Democratic Republic of Congo, Lesotho, and Swaziland where reliance on trade taxes is the highest in the world. In 2007-08, receipts from the Southern African Customs Union (SACU) exceeded half of total revenues in Swaziland, the country most reliant on trade taxes in 2007-08. Trade taxes in Botswana make up a lower share of government revenues but that is principally due to high resource-related tax revenues. Its trade taxes as a share of government revenues still exceed the sub-Saharan African average (Keen and Mansour, 2009).

To put these observations in perspective, Keen and Mansour (ibid.) show that between 1980-82 and 2003-05, of the 40 countries they cover, 30 countries have lower trade taxes as a share of GDP, down on average from 7.4% to 4.2%. Only 10 countries have gained, on average from 3.2% to 4.8%. Between the early 1980s and 2005, the same authors argue that the average collected tariff rate, defined as tariff revenues divided by imports in value, has gone down in sub-Saharan Africa from above 20% to below 13%.