This document is the data and definitions appendix to the 2010 Report on Illinois Poverty report which caps a decade of Heartland Alliance's annual reports on poverty. The project was initiated at a time when economic prosperity seemed widespread and the future outlook was infused with optimism. The goal with these reports at that time was simple: to serve as a caution that the rising tide of prosperity in the late 1990s had not lifted all boats and that many in our communities were being left behind. Today the situation is very different. The Great Recession has crumbled economic stability for millions of families in the form of massive job loss, cut backs in hours, the elimination of work benefits, skyrocketing foreclosures and bankruptcies, and the eroding value of retirement investments. The implications of massive service cuts to those experiencing poverty -- many of whom rely on state-funded services in their communities literally for survival, particularly those in extreme poverty -- will be nothing short of devastating. Without leadership to enact a responsible budget, Illinois can expect to see deepening hardship and further entrenchment of social problems.