base period

American  

noun

1. a period of time used as a standard of comparison in measuring changes in prices, taxes, income, etc., at other periods of time.

---

base period British  

noun

1. statistics a neutral period used as a standard for comparison in constructing an index to express a variable factor: 100 is usually taken as the index number for the variable in the base period

---

Example Sentences

The Bureau’s consumer price index average for all items shows that over the past 50 years, the years 1982-84 provide the base period for $100.

From Washington Times • Jun. 4, 2017

Known as the Integrated Fixed Tower contract, it includes a base period quantity and options that CBP may exercise over several years.

From Reuters • Mar. 2, 2014

Currently, CBP awarded the base period quantity for a portion of the $145 million total contract amount, to be implemented over one year, Elbit said on Sunday.

From Reuters • Mar. 2, 2014

Then the tax would be raised another nickel or maybe even a dime for every year in which gas usage failed to drop at least 2% from the base period.

From Time Magazine Archive

Thereafter, the gas tax would be automatically increased by 50 at the end of any year in which total consumption rose more than 1% above the base period.

From Time Magazine Archive