A recent World Bank/Water and Sanitation Program initiative on the economics of sanitation in 18 countries in Sub-Saharan Africa found that:
Inadequate sanitation costs [these] 18 African countries around US$5.5 billion each year [around 1−2.5% of GDP].
Open defecation alone accounts for almost US$2 billion of these annual losses in the[se] 18 countries. Lacking alternatives, more than 114 million people still defecate in the open in the 18 countries surveyed − this is about half the number of people on the continent and almost 24% of the total population in the countries surveyed. Eliminating the practice of open defecation in these countries would require about 23 million toilets to be built and used.
Each of the 18 countries has its own report (downloadable here). Fairly grim reading – but, of course, unfortunately what we're used to. Will sanitation ever get the real priority it deserves?