Time price
The quantity of work time required to earn the money to buy one unit of a good or service. The nominal price of the good divided by the nominal hourly wage. Expressed in minutes or hours.
Nominal price
The price as denominated and transacted in the currency of the day, before any inflation adjustment. The TPI-US 25 uses nominal US dollar prices from primary sources without deflation.
Wage denominator
The hourly wage series used to convert nominal prices into time prices. For the TPI-US 25 the wage denominator is the annual average of the AHETPI monthly series.
AHETPI
FRED series identifier for Average Hourly Earnings of Production and Nonsupervisory Employees, Total Private. Published monthly by the US Bureau of Labor Statistics since January 1964 from the Current Employment Statistics establishment survey. Excludes managerial and supervisory pay.
Base year
The reference year against which other years' index values are scaled. The TPI-US 25 base year is 1980, set to an index value of 100. All subsequent annual values express the basket time price relative to its 1980 level.
Constituent
A single good or service included in the basket. Each constituent has a stable unit of measurement, a primary-source nominal price series covering 1980 to the current reporting year, and a documented source citation.
Basket
The fixed set of 25 constituents whose mean time price defines the index. The basket is selected at index inception under the basket selection rules and is not rebalanced on a schedule.
Abundance multiplier
The ratio of the base-year basket time price to the current basket time price. A multiplier of 3.6× indicates that the basket today requires 3.6 times less work time than it did in 1980.
Equal weighting
Each constituent contributes equally to the basket mean. The TPI-US 25 uses equal weighting rather than expenditure weighting, treating each item as an independent affordability probe rather than a stand-in for a representative consumption bundle.
Quality adjustment
Substitution of a hedonic-quality-adjusted CPI subindex for a constituent whose physical characteristics have changed substantially over the index history. The TPI-US 25 applies quality adjustment only to the personal computer and mobile phone constituents, anchored to a 1980 reference unit price.
Rebalance
A change to the basket composition, typically the replacement of a constituent whose primary source has ceased publication or whose underlying good is no longer purchased at meaningful scale. Each rebalance is recorded in the changelog, and the historical index is recomputed with the replacement constituent backfilled to 1980 to preserve the chain.
Time price vs. real price
A real price deflates a nominal price by a price index, expressing it in constant-purchasing-power currency. A time price divides a nominal price by an hourly wage, expressing it in units of work time. Real prices ask how much the currency has lost in value; time prices ask how much an hour of work has gained in purchasing power.
Time price vs. CPI inflation
CPI tracks expenditure-weighted prices of a consumption basket designed to represent average household spending. The TPI-US 25 tracks an equal-weighted basket of 25 items as time prices. The two series move differently when wages outpace prices, when basket composition diverges from CPI weights, or when quality adjustments differ.