An automatic annual Social Security benefit increase is intended to reflect the rise in the cost of living over a one-year period. The Consumer Price Index for Urban Wage Earners and Clerical Workers (CPI-W), updated monthly by the Bureau of Labor Statistics (BLS), is the measure that can trigger a benefit increase. The Social Security cost-of-living adjustment (COLA) is based on the growth in the index from the highest third calendar quarter average CPI-W recorded (most often, from the previous year) to the average CPI-W for the third calendar quarter of the current year. If the CPI-W triggers a COLA, the COLA becomes effective in December of the current year and is payable in January of the following year. (Social Security payments always reflect the benefits due for the preceding month.) A COLA trigger mechanism was first adopted in P.L. 92-603, the Social Security Amendments of 1972, and triggered COLAs were first payable in 1975. Prior to 1975, Congress sporadically approved COLAs through the adoption of legislation. On October 11, 2018, the Social Security Administration (SSA) announced that a 2.8% Social Security COLA would be paid in January 2019. The BLS release of the September 2018 CPI-W on that day made possible the comparison of the two July-September sets of CPI-W data needed to compute the COLA (one for 2017 and another for 2016). Table 1 shows how the determination for a January 2019 COLA is computed under procedures set forth in Section 215(i) of the Social Security Act. Since automatic Social Security benefit COLAs began in 1975, there have been three years in which no COLA was payable: 2010, 2011, and 2016. The Social Security Act specifies that a COLA is payable automatically if the average CPI-W for the third quarter of the current year is higher than the highest average CPI-W for the third quarter of past years, which is called the "cost-of-living computation quarter." From 1975, when this provision became effective, to 2008, a new cost-of-living computation quarter was established in each subsequent year, which triggered the payment of a COLA each year. If the average CPI-W for the third quarter of the current year is equal to or less than the average CPI-W for the cost-of-living computation quarter, no COLA is payable. For example, the average CPI-W for the third quarter of 2009 was less than the average CPI-W for the third quarter of 2008 (211.001 and 215.495, respectively). As a result, an automatic COLA in January 2010 was not triggered and the third quarter of 2008 remained the cost-of-living computation quarter (i.e., the benchmark) used to determine if a COLA would be payable in January 2011. Though the average CPI-W for the third quarter of 2010 (214.136) was greater than the average CPI-W for the third quarter of 2009, it did not exceed the average CPI-W for the third quarter of 2008. The third quarter of 2008 remained the cost-of-living computation quarter for at least one more year and a COLA was not payable in January 2011. When the average CPI-W for the third quarter of 2011 (223.233) exceeded that for 2008, a 2012 COLA was triggered and the third quarter of 2011 became the cost-of-living computation quarter. New cost-of-living computation quarters were subsequently established in each year from 2012 to 2014, when the average CPI-W for the third quarter of 2012, 2013, and 2014 exceeded that for the third quarter of each preceding year. Similarly, since the average CPI-W for the third quarter of 2015 (233.278) did not exceed that of 2014 (234.242), no COLA was paid in January 2016. Thus, for the COLA payable beginning in January 2017, the cost-of-living computation benchmark quarter remained the third quarter of 2014 where it was compared with the average CPI-W for the third quarter of 2016. See Table 2 for a recent history of average CPI-W performance for the third calendar quarter, and how that has affected changes to the cost-of-living computation quarter and the triggering of COLAs in some years. Social Security benefit amounts cannot be reduced if the CPI-W decreases between the measuring periods. If the performance of the CPI-W does not trigger a COLA, benefits remain the same (prior to deductions for Medicare Part B and Part D premiums). The absence of a COLA increase (or a very small increase) may impact certain Medicare Part B enrollees. For Medicare Part B enrollees who have their Part B premiums withheld from their monthly Social Security benefits, a hold-harmless provision in the Social Security Act (SS1839[f]) ensures that their net benefits will not decrease as a result of an increase in the Part B premium. In most years, the hold-harmless provision has little impact; however, in a year in which there is a small or no increase in the Social Security COLA and a Part B premium increase, the hold-harmless provision may apply to a much larger number of people. For example, as a result of a 0% Social Security COLA in 2016 and a 0.3% COLA in 2017, an estimated 70% of Medicare beneficiaries were protected by this provision in those years and their premiums were reduced so that their Social Security benefits, net of the Medicare premium, would not decline. As a result of the relatively higher 2.0% Social Security COLA in 2018, the hold-harmless provision was not as broadly applicable in that year, and the percentage of Medicare Part B enrollees held harmless in 2018 declined to 28%. The Medicare trustees project that 2019 Medicare Part B premiums will increase by about $1.50 per month--from $134.00 per month in 2018 to about $135.50 in 2019. Under this scenario, the 2019 2.8% Social Security COLA would likely result in a further reduction in the number of Medicare Part B enrollees held harmless. In most cases, the dollar amount of the increase in enrollees' Social Security benefits, for both those who were and were not held harmless in 2018, would be more than sufficient to cover their 2019 Part B premium increases. Thus, it is likely that many of those held harmless in 2018 will not be held harmless in 2019 and will return to paying the normal standard premium amount. The actual 2019 Medicare premiums will likely be announced later in 2018 and could be higher or lower than projected. Regardless of the size (or absence) of a COLA, beneficiaries may see a net reduction in Social Security benefits as a result of increases in their Medicare Part D premiums or changes in their Medicare Part D plan selections. Social Security COLAs trigger increases in other programs. Supplemental Security Income (SSI) benefits and railroad retirement "tier 1" benefits (equivalent to a Social Security benefit) are increased by the same percentage as the Social Security COLA or are held constant when a COLA is not paid to Social Security beneficiaries. Railroad retirement "tier 2" benefits (equivalent to a private pension) are increased by an amount equivalent to 32.5% of the Social Security COLA. (If no COLA is paid to Social Security beneficiaries, then the railroad retirement tier 2 benefits are not increased.) Veterans' pension benefits often are increased in the same amount as Social Security, but legislation must be passed annually for this purpose. Although COLAs under the Civil Service Retirement System (CSRS) and the federal military retirement system are not triggered by the Social Security COLA, these programs use the same measuring period and formula for determining their COLAs. The COLA for recipients of Federal Employees' Retirement System (FERS) benefits equals the Social Security COLA if inflation is 2% or less, but is lower than the Social Security COLA otherwise. Some Social Security program elements, like the taxable earnings base , the retirement earnings test (RET) exempt amounts , and the substantial gainful activity (SGA) earnings level for the blind (which applies to Social Security disability beneficiaries), are indexed to wages, as opposed to prices, but increase only when a COLA is payable. Although changes to those three elements are based on growth in national average wages (rather than changes in prices ), these elements can be increased only when a COLA is payable. If a COLA is payable, then these amounts increase by the percentage that the national average wage index has increased. The taxable earnings base, the RET exempt amounts, and the SGA for the blind were unchanged in 2010, 2011, and 2016 when no COLA was payable. For example, had there been a COLA trigger in 2015, the taxable earnings base would have increased from $118,500 in 2015 to $122,700 in 2016. Because there was no COLA trigger in 2015, the base instead remained unchanged. With the 0.3% COLA announced in 2016, the taxable earnings base increased in 2017 as well. Similar to how the COLA's reference period is calculated, the increase in the taxable earnings base is calculated on the increase in the average wage index from 2013 to 2015 (about 7.2%). Table 3 shows the history of Social Security COLAs since the automatic COLAs began in 1975. Table 4 provides a comprehensive summary of all ad-hoc legislative cost-of-living adjustments to Social Security benefits before automatic adjustments began in July 1975. The first increase occurred in October 1950, 10 years after Social Security benefits were first issued in 1940. At that time, Social Security benefits were increased by 77%. After 1950, smaller increases were granted by separate legislation at irregular intervals. Table 4 shows the percentage increases and the dates from which these increases were paid. As noted, in 1974 the increase occurred in two steps: an increase of 7% was paid from April 1974 until June 1974; and an increase of 11% was paid from July 1974 onward. Both increases used February 1974 as the base level. Authorization for the automatic benefit increase beginning in 1975 appears as part of P.L. 92-336.

Summary:
To compensate for the effects of inflation, Social Security recipients usually receive an annual cost-of-living adjustment (COLA). According to parameters outlined in the Social Security Act (42 U.S.C. 415(i)), a 2.8% COLA is payable in January 2019. For a retired worker receiving the average monthly benefit amount of $1,422, the COLA will result in a $39 increase in Social Security benefits (after final rounding down to the nearest dollar for a total of $1,461). Social Security COLAs are based on changes in the Consumer Price Index for Urban Wage Earners and Clerical Workers (CPI-W), updated monthly by the Department of Labor's Bureau of Labor Statistics (BLS). The COLA equals the growth, if any, in the index from the highest third calendar quarter average CPI-W recorded (most often, from the previous year) to the average CPI-W for the third calendar quarter of the current year. The COLA becomes effective in December of the current year and is payable in January of the following year. (Social Security payments always reflect the benefits due for the preceding month.) If there is no percentage increase in the CPI-W between the measuring periods, no COLA is payable. No COLA was payable in January 2010, January 2011, or in January 2016. The January 2019 COLA will also be applied to Supplemental Security Income (SSI) and railroad retirement "tier 1" benefits, among other changes in the Social Security program. Although COLAs under the federal Civil Service Retirement System (CSRS) and the federal military retirement program are not triggered directly by the Social Security COLA, these programs use the same measuring period and formula for computing their COLAs. As a result, their recipients will receive a similar COLA payable in 2019.