If current population and consumption trends continue, Africa's Ecological Footprint will exceed its biocapacity within the next twenty years, while a number of countries, including Senegal, Kenya and Tanzania, are set to reach that threshold in less than five years, according to a report issued today by Global Footprint Network and key partners.
I found this page to be a useful tool to show students the complexity of determining levels of development. In addition, if you hover the mouse over the link you get a definition!