In Mauritania , the last country to abolish slavery (in 1981),  it is estimated that up to 600,000 men, women and children, or 20% of the population, are enslaved with many used as bonded labour .    Slavery in Mauritania was criminalized in August 2007.  (although slavery as a practice was legally banned in 1981, it was not a crime to own a slave until 2007).  Although many slaves have escaped or have been freed since 2007, as of 2012 [update] , only one slave-owner had been sentenced to serve time in prison. 
This timeline was prepared for NHD Philly , the regional National History Day program for Philadelphia, Pennsylvania. It is a collaboration of more than thirty history and community-based organizations in the Greater Philadelphia region. The participating partners represent some of the most significant history collections and programs in the United States, as well as the region's extensive community of education and heritage tourism enterprises. In addition to the regional National History Day Competition, the collaboration provides programs and products that support not only learning history, but also the development of research and analytical skills through the exploration of special collections, archives, museums and historic sites.