Cost of living

Cost of living is the cost of maintaining a certain standard of living. Changes in the cost of living over time are often operationalized in a cost of living index. Cost of living calculations are also used to compare the cost of maintaining a certain standard of living in different geographic areas. Differences in cost of living between locations can also be measured in terms of purchasing power parity rates.

Employment contracts, pension benefits, and government entitlements such as Social Security can be tied to a cost-of-living index, typically to the consumer price index (CPI). A COLA adjusts salaries based on changes in a cost-of-living index. Salaries are typically adjusted annually. They may also be tied to a cost-of-living index that varies by geographic location if the employee moves. In this later case, the expatriate employee will likely see only the discretionary income part of their salary indexed by a differential CPI between the new and old employment locations, leaving the non-discretionary part of the salary (e.g., mortgage payments, insurance, car payments) unmodified.

Annual escalation clauses in employment contracts can specify retroactive or future percentage increases in worker pay which are not tied to any index. These negotiated increases in pay are colloquially referred to as cost-of-living adjustments or cost-of-living increases because of their similarity to increases tied to externally determined indexes. Cost-of-living allowance is equal to the nominal interest minus the real interest rate.

When cost-of-living adjustments, negotiated wage settlements and budgetary increases exceed CPI, media reports frequently compare the two without consideration of the pertinent tax code. However, CPI is based on the retail pricing of a basket of goods and services. Most purchases of that same basket require the use of after-tax dollars—dollars that were often subject to the highest marginal tax rate. Consequently, the COLA will necessarily have to exceed the CPI inflation rate to maintain purchasing power.

The widely recognized problem known as bracket-creep can also occur in countries where the marginal tax brackets themselves are not indexed—COLA increases simply place more dollars into higher tax rate brackets. (Only under a flat tax system would a percentage gain on gross income translate into a comparable inflation-offsetting gain at the after-tax level.)

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