Colorado once had a stellar record of responsibly supporting its pension plans—but that fell apart in recent years. The state experienced one of the most severe drops in pension funding levels of any state in the early years of the decade, and between 2003 and 2006, the amount of money the state contributed to its pension systems fell far short of annual required contributions. Colorado was particularly vulnerable to the weakening economy because it had a very high percentage of pension funds invested in stocks and real estate investment trusts in the late 1990s. The state subsequently changed its asset allocation practices and now they track more closely with other states. The pension system also suffered from pressures stemming from the state's Taxpayers Bill of Rights (TABOR). Colorado has passed a number of significant pension reforms in recent years. To its credit, it was one of just 13 states at the end of 2006 that had set aside some money to cover the cost of health care benefits for future retirees.