Unlike income brackets that are adjusted annually, the income thresholds that subject Social Security income to taxation are fixed. Because of this, the number of Social Security recipients who are hit by the tax has increased substantially over the years as incomes have grown. .New Social Security COLA Legislation Introduced .However, statistics indicate that unauthorized immigrants from Mexico make up a majority of all unauthorized immigrants in the U.S., and in a 2003 report, the General Accounting Office (GAO, now known as the Government Accountability Office) recognized the potential for unauthorized immigrant workers to abuse the Social Security system and fraudulently obtain benefits. .Cost-of-living increases are based on the nation's general rate of inflation, and the prices for the goods and services used to calculate inflation have barely budged. .The Congressional Budget Office (CBO) and the Joint Committee on Taxation have boosted previous estimates and now say that switching to the chained consumer price index (C-CPI) will cut Social Security and other federal retirement benefits by 8 billion and increase taxes by 2 billion over the next 10 years. The loss to beneficiaries would compound over time and grows deeper each year as illustrated in the following chart. As seniors grow older and more likely to develop costly health conditions, their Social Security benefits would become less adequate to cover rising costs more quickly. . Four Key Bills Gain Support in Congress .The total revenues in the sample could pay the Social Security benefits of 897 retirees, with an average monthly benefit of ,400, for an entire year. Or, that revenue could be used to provide a modest boost to the COLA of 448,560 retirees in the first year, by tying the annual inflation adjustment to the Consumer Price Index for the Elderly (CPI-E). .Part B premiums are only part of what Medicare recipients pay. People also have premiums for a Medigap supplement and Part D plan, or a Medicare Advantage plan and those premiums are rising as well. Hold harmless protection does not apply to premium increases in these private plans, and any increase would leave retirees .The Centers for Medicare and Medicaid Services (CMS) has estimated that it improperly paid .1 billion to Medicare Advantage plans in 2013 alone. Yet the plans are rarely forced to repay the money they have overcharged, or face closer government scrutiny after the audits, according to the Government Accountability Office (GAO). The GAO report said that CMS has failed to target health plans with "known improper payment risk", allowing the worst abusers to avoid scrutiny.