What proportion of Sub-Saharan Africa's countries have lower middle incomes?
proportion = divide(count(countrycode where incomegroup = 'Low income'), count(countrycode))*100%; Sub-Saharan Africa's countries refers to region = 'Sub-Saharan Africa'; have lower middle incomes refers to incomegroup = 'Low income'
SELECT SUM(CASE WHEN IncomeGroup = 'Lower middle income' THEN 1 ELSE 0 END) * 100.0 / COUNT(CountryCode) persentage FROM Country WHERE Region = 'Sub-Saharan Africa'