A joint study by the World Bank and AFD carried out by Alain Mingat, Blandine Ledoux and Ramahatra Rakotomalala sought to anticipate the pressures that would be brought to bear on post-primary teaching. The study puts it this way: "“In the reference year" "(2005), our sample of 33 countries in sub-Saharan Africa had 14.9 million pupils enrolled in the first year of secondary school. If the rate of completion of the primary stage reaches 95% by 2020 with levels of transition from primary to the first year of secondary maintained at their current level in each country, the first year of secondary school would have 37.2 million pupils in 2020, or 2.5 times the current number. If all the pupils finishing primary school could continue with their education, the number of pupils in the first year of secondary school would reach 62.9 million by 2020, a multiplication by 4.2 over the period.”" Behind the regional averages, there are still enormous disparities between the countries, and even between the different zones and regions within countries, which means that it is not possible to “[…] identify conditions that apply uniformly to education across the different countries of sub-Saharan Africa.” While some countries have lower demographic growth, others enjoy a more satisfactory level of school enrolment. Only a few countries are falling seriously behind in education at the same time as having to address a steady growth in their school-age population: Niger, Eritrea, Burundi, Guinea-Bissau, Uganda and to a lesser extent Burkina Faso, Chad, Mali, Mozambique, Rwanda, Senegal and Malawi are particularly affected by this dual constraint. The EFA 2012 report highlights great disparities between the sub-Saharan African countries: the percentage of children excluded from primary school is only 7% in Gabon and 14% in Congo compared to over 55% in Burkina Faso and Niger. The gap in terms of the proportion of those excluded from the first year of middle school is even wider, with 6% in Gabon compared to 68% in Burkina Faso and 73% in Niger.