While the issue on the existence of shadow education institutions (SEI's) has only recently been the subject of investigation in studies in various countries worldwide, it is clear that its market is a huge industry in much of Asia and is growing fast elsewhere. Capitalizing on the annual number of SEI's gathered from key government agencies and processed through time series analysis, this paper purports to establish hard data on shadow education proliferation (1980-2011) in the Philippines with a view of providing valuable insights to both business and educational management areas and to policy makers. Trend analysis showed that prior to 1980, the number of SEI's established per year was negligible but has gained momentum from 1996 to 2004. Apparently, variability in the number of SEI's established each year shall depend on certain business regulation policies of the government, the quality of mainstream education in the country, and workplace competition.