How BLS Measures Price Change for Airline Fares in the Consumer Price Index
The Consumer Price Index (CPI) has included Airline Fares as a component of the Public
Transportation index since December 1963. The Public Transportation index is published in all
CPI publication areas on each area's publication cycle. The Airline Fares index is published
monthly at the U.S. level and is also seasonally adjusted.
Eligible for pricing are all regularly scheduled domestic and international commercial
airline trips on certified carriers departing from each of the 87 cities in the CPI sample.
For the selected cities that do not have a qualifying airport, the nearest city with a
qualifying airport is designated as the city of departure.
Excluded from pricing are trips in helicopters, trips on intra-Alaska carriers, and trips
designated as business travel.
The relative importance of an item category is its percent of the CPI weight as of December
of the most recent year. The airline fares index relative importance of 0.699 (Table 1)
signifies that it represented 0.699% of the All Items index as of December 2015.
Table 1: Relative Importance of Public Transportation components of the CPI for All
Urban Consumers (CPI-U): U.S. city average, December 2015
| Airline fares
| Other inter-city public transportation
| Intra-city public transportation
|| Unsampled public transportation
BLS selects approximately 1100 observations each month for its airline fares index. This sample
represents the non-business airline travel of the U.S. urban population.
In each of the 87 CPI pricing areas, a sample of trips is selected for pricing using those
cities as the points of origin. The specific trips to be priced are selected with probability
proportional to the number of passengers on each trip included on the U.S. Department of
Transportation (DOT) data bank.
DOT data contain 10 percent of tickets sold by certified air carriers in
scheduled passenger service. Each record on the data tape includes all relevant information
about the particular trip in question. Included are such variables as points of origin and
destination, airline, class of service, and fare (First Class, Coach Full Fare, Coach Discount
Fare). The DOT data does not provide descriptions for specific discounts.
Reflecting the pattern of trips in the DOT data, the CPI sample of airline trips selected from DOT consists largely of discount fare service: 94 percent of the observations for discount service, 4 percent for full coach, and 2 percent for first class service. There are normally several discount fares for a given trip. Of the quotes priced for discount service, BLS assigns approximately half for the lowest available discount fare. The remaining half is for specific discount fares other than the lowest available fare.
Pricing the lowest available fare for half of the discount sample provides for an appropriate reflection of industry-wide sales typically referred to as "fare wars." Usually these deeply discounted fares are limited to the lowest available fare for a given trip. As seating for the lowest available fares is limited, BLS collects quotes for specifically selected discount fares other than the lowest available fare for the remainder of the sample.
Frequent Flyer discounts are not included in the index.
Web-based pricing enables the CPI to track a more
defined trip month-to-month, where prices are collected by assigning each quote fixed specifications for advance
reservation and day of the week. Each month the same advance reservation specification (designated by number of weeks) and day of the week specification
will be used to collect a price. For example, a quote with a "seven week" advance reservation specification and "Tuesday" as the day of the week
specification will always be priced as if the consumer booked airfare in the current month for departure seven weeks in advance on a Tuesday. This method
enables the CPI to price a more consistently defined trip each month in addition to more accurately emulating how consumers book airfare.
Roughly 1/5 of the sample is priced monthly (in the monthly cities) and the rest of the sample is priced bi-monthly. Prices include all applicable
taxes, domestic and international. Fuel Surcharges, Airport, Security, and baggage fees are also included. Care is taken to spread pricing evenly
throughout the month to give appropriate representation to price trends occurring throughout the month.
When an airline discontinues a discount fare that is being priced, BLS
substitutes the closest available alternative. Applicable restrictions may
change, such as time of departure, connecting airports, or number of layovers. When such changes occur, BLS estimates
the value of the change. If the value of the change in quality is substantial, the prices for two discount fares in question will not be compared. In most
cases, however, the quality difference between two such discount fares is considered trivial and the prices are compared and reflected in the CPI.
Additional information on the Consumer Price Index
can be found in the BLS Handbook of Methods,
chapter 17, "The Consumer Price Index,".
This chapter is also available on the BLS Internet site
(www.bls.gov/opub/hom/pdf/homch17.pdf). For more information, call the Information and Analysis Section of the CPI at (202) 691-7000.
Last Modified Date: May 26, 2016