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Economic News Release
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CPI CPI Program Links

Consumer Price Index Summary



Transmission of material in this release is embargoed until                                        
8:30 a.m. (ET) October 13, 2021             USDL-21-1831

Technical information: (202) 691-7000  •  cpi_info@bls.gov  •  www.bls.gov/cpi
Media Contact:         (202) 691-5902  •  PressOffice@bls.gov 

CONSUMER PRICE INDEX – SEPTEMBER 2021

The Consumer Price Index for All Urban Consumers (CPI-U) increased 0.4 percent in
September on a seasonally adjusted basis after rising 0.3 percent in August, the
U.S. Bureau of Labor Statistics reported today. Over the last 12 months, the all
items index increased 5.4 percent before seasonal adjustment.

The indexes for food and shelter rose in September and together contributed more
than half of the monthly all items seasonally adjusted increase. The index for
food rose 0.9 percent, with the index for food at home increasing 1.2 percent.
The energy index increased 1.3 percent, with the gasoline index rising
1.2 percent.

The index for all items less food and energy rose 0.2 percent in September,
after increasing 0.1 percent in August. Along with the index for shelter, the
indexes for new vehicles, household furnishings and operations, and motor
vehicle insurance also rose in September. The indexes for airline fares, apparel,
and used cars and trucks all declined over the month.  

The all items index rose 5.4 percent for the 12 months ending September, compared
to a 5.3-percent rise for the period ending August. The index for all items less
food and energy rose 4.0 percent over the last 12 months, the same increase as
the period ending August. The energy index rose 24.8 percent over the last 12
months, and the food index increased 4.6 percent over that period. 


Table A. Percent changes in CPI for All Urban Consumers (CPI-U): U.S. city average

                                  Seasonally adjusted changes from
                                          preceding month
                                                                          Un-
                                                                       adjusted
                                                                        12-mos.
                              Mar.  Apr.  May   June  July  Aug.  Sep.   ended
                              2021  2021  2021  2021  2021  2021  2021   Sep.
                                                                         2021

 All items..................    .6    .8    .6    .9    .5    .3    .4      5.4
  Food......................    .1    .4    .4    .8    .7    .4    .9      4.6
   Food at home.............    .1    .4    .4    .8    .7    .4   1.2      4.5
   Food away from home (1)..    .1    .3    .6    .7    .8    .4    .5      4.7
  Energy....................   5.0   -.1    .0   1.5   1.6   2.0   1.3     24.8
   Energy commodities.......   8.9  -1.4   -.6   2.6   2.3   2.7   1.3     41.7
    Gasoline (all types)....   9.1  -1.4   -.7   2.5   2.4   2.8   1.2     42.1
    Fuel oil (1)............   3.2  -3.2   2.1   2.9    .6  -2.1   3.9     42.6
   Energy services..........    .6   1.5    .7    .2    .8   1.1   1.2      8.5
    Electricity.............    .0   1.2    .3   -.3    .4   1.0    .8      5.2
    Utility (piped) gas
       service..............   2.5   2.4   1.7   1.7   2.2   1.6   2.7     20.6
  All items less food and
     energy.................    .3    .9    .7    .9    .3    .1    .2      4.0
   Commodities less food and
      energy commodities....    .1   2.0   1.8   2.2    .5    .3    .2      7.3
    New vehicles............    .0    .5   1.6   2.0   1.7   1.2   1.3      8.7
    Used cars and trucks....    .5  10.0   7.3  10.5    .2  -1.5   -.7     24.4
    Apparel.................   -.3    .3   1.2    .7    .0    .4  -1.1      3.4
    Medical care
       commodities (1)......    .1    .6    .0   -.4    .2   -.2    .3     -1.6
   Services less energy
      services..............    .4    .5    .4    .4    .3    .0    .2      2.9
    Shelter.................    .3    .4    .3    .5    .4    .2    .4      3.2
    Transportation services    1.8   2.9   1.5   1.5  -1.1  -2.3   -.5      4.4
    Medical care services...    .1    .0   -.1    .0    .3    .3   -.1       .9

   1 Not seasonally adjusted.


Food

The food index increased 0.9 percent in September, following a smaller 0.4-percent
increase in August. The food at home index increased 1.2 percent over the month as
all six major grocery store food group indexes rose. The index for meats, poultry,
fish, and eggs rose 2.2 percent over the month as the index for beef rose
4.8 percent. The index for other food at home increased 1.1 percent in September
after rising 0.6 percent in August. The index for nonalcoholic beverages increased
1.2 percent in September, its fourth consecutive monthly increase. The index for
fruits and vegetables rose 0.6 percent in September, a larger increase than the
0.2-percent increase reported in August. The index for cereals and bakery products
increased 1.1 percent over the month, while the index for dairy and related
products rose 0.7 percent.

The food away from home index rose 0.5 percent in September after increasing
0.4 percent in August. The indexes for limited service meals and for full service
meals both increased 0.6 percent in September. These increases offset a decline
in the index for food at employee sites and schools, which continued to fall,
decreasing 6.4 percent in September.

The food at home index rose 4.5 percent over the past 12 months as all of the six
major grocery store food group indexes increased over the period. The largest
increase was the index for meats, poultry, fish, and eggs, which increased
10.5 percent as the index for beef rose 17.6 percent over the year. The smallest
increase was the dairy and related products index, which rose 0.6 percent over the
last 12 months. The index for food away from home rose 4.7 percent over the last
year. The index for limited service meals rose 6.7 percent over the last 12 months,
and the index for full service meals rose 5.2 percent, while the index for food at
employee sites and schools declined sharply.  

Energy

The energy index rose 1.3 percent in September, its fourth consecutive monthly
increase. The gasoline index rose 1.2 percent in September after increasing
2.8 percent in August. (Before seasonal adjustment, gasoline prices rose
0.3 percent in September.) The electricity index increased 0.8 percent in
September following a 1.0-percent increase the prior month. The index for natural
gas also increased in September, rising 2.7 percent; this was its eighth
consecutive monthly increase.  

The energy index rose 24.8 percent over the past 12 months as all the major energy
component indexes increased. The gasoline index rose 42.1 percent over the last
year. The index for electricity increased 5.2 percent and the index for natural
gas rose 20.6 percent over the last 12 months.

All items less food and energy

The index for all items less food and energy rose 0.2 percent in September. The
shelter index increased over the month, rising 0.4 percent. The index for rent
rose 0.5 percent in September, while the index for owners’ equivalent rent rose
0.4 percent over the month. Other indexes that increased over the month include
the index for new vehicles, which rose 1.3 percent following a 1.2-percent
increase the previous month; and the index for household furnishings and
operations, which increased 1.0 percent in September as the indexes for furniture
and bedding and for appliances rose. 

The motor vehicle insurance index rose 2.1 percent in September, after falling
2.8 percent in August. The index for communication and the index for education
both increased 0.4 percent over the month. The recreation index rose 0.2 percent
in September after increasing 0.5 percent the prior month. 

In contrast to these increases, several indexes declined in September. The index
for airline fares continued to fall sharply, decreasing 6.4 percent over the month
after falling 9.1 percent in August. The apparel index also decreased in September,
declining 1.1 percent over the month after rising 0.4 percent in the previous
month. The index for used cars and trucks fell 0.7 percent this month, continuing
to decline after it decreased 1.5 percent in August.

The medical care index was unchanged in September, with its component indexes
mixed. The index for prescription drugs rose 0.8 percent over the month and the
index for hospital services increased 0.1 percent. In contrast, the physicians’
services index declined 0.3 percent in September. 

The index for all items less food and energy rose 4.0 percent over the past
12 months. The index for used cars and trucks increased 24.4 percent over the
span. The index for new vehicles rose 8.7 percent, the largest 12-month increase
since the period ending September 1980. The shelter index increased 3.2 percent
over the last 12 months, and the household furnishings and operations index rose
5.1 percent. The index for medical care rose 0.4 percent over the last year, with
the index for physicians’ services rising 3.8 percent and the index for hospital
services increasing 3.2 percent. The prescription drugs index fell 1.6 percent,
one of the few indexes to show a 12-month decline. 

Not seasonally adjusted CPI measures

The Consumer Price Index for All Urban Consumers (CPI-U) increased 5.4 percent
over the last 12 months to an index level of 274.310 (1982-84=100). For the month,
the index increased 0.3 percent prior to seasonal adjustment.  

The Consumer Price Index for Urban Wage Earners and Clerical Workers (CPI-W)
increased 5.9 percent over the last 12 months to an index level of 269.086
(1982-84=100). For the month, the index rose 0.3 percent prior to seasonal
adjustment.  

The Chained Consumer Price Index for All Urban Consumers (C-CPI-U) increased
5.3 percent over the last 12 months. For the month, the index increased
0.3 percent on a not seasonally adjusted basis. Please note that the indexes
for the past 10 to 12 months are subject to revision. 
_______________
The Consumer Price Index for October 2021 is scheduled to be released on Wednesday,
November 10, 2021 at 8:30 a.m. (ET).

--------------------------------------------------------------------------------------------------
 Coronavirus (COVID-19) Pandemic Impact on September 2021 Consumer Price Index Data

 Data collection by personal visit for the Consumer Price Index (CPI) program has been suspended
 since March 16, 2020. When possible, data normally collected by personal visit were collected either
 online or by phone. Additionally, data collection in September was affected by the temporary closing or
 limited operations of certain types of establishments. These factors resulted in an increase in the
 number of prices considered temporarily unavailable and imputed. While the CPI program attempted to
 collect as much data as possible, many indexes are based on smaller amounts of collected prices
 than usual, and a small number of indexes that are normally published were not published this month.
 Additional information is available at
 www.bls.gov/covid19/effects-of-covid-19-pandemic-on-consumer-price-index.htm.
 
----------------------------------------------------------------------------------------------------



Technical Note

Brief Explanation of the CPI

The Consumer Price Index (CPI) measures the change in prices paid by consumers
for goods and services. The CPI reflects spending patterns for each of two
population groups: all urban consumers and urban wage earners and clerical
workers. The all urban consumer group represents about 93 percent of the total
U.S. population. It is based on the expenditures of almost all residents of urban
or metropolitan areas, including professionals, the self-employed, the poor,
the unemployed, and retired people, as well as urban wage earners and clerical
workers. Not included in the CPI are the spending patterns of people living in
rural nonmetropolitan areas, farming families, people in the Armed Forces, and
those in institutions, such as prisons and mental hospitals. Consumer inflation
for all urban consumers is measured by two indexes, namely, the Consumer Price
Index for All Urban Consumers (CPI-U) and the Chained Consumer Price Index for
All Urban Consumers (C-CPI-U).

The Consumer Price Index for Urban Wage Earners and Clerical Workers (CPI-W)
is based on the expenditures of households included in the CPI-U definition
that meet two requirements: more than one-half of the household's income must
come from clerical or wage occupations, and at least one of the household's
earners must have been employed for at least 37 weeks during the previous
12 months. The CPI-W population represents about 29 percent of the total U.S.
population and is a subset of the CPI-U population.

The CPIs are based on prices of food, clothing, shelter, fuels, transportation,
doctors’ and dentists’ services, drugs, and other goods and services that people
buy for day-to-day living. Prices are collected each month in 75 urban areas
across the country from about 6,000 housing units and approximately 22,000 retail
establishments (department stores, supermarkets, hospitals, filling stations, and
other types of stores and service establishments). All taxes directly associated
with the purchase and use of items are included in the index. Prices of fuels and
a few other items are obtained every month in all 75 locations. Prices of most
other commodities and services are collected every month in the three largest
geographic areas and every other month in other areas. Prices of most goods and
services are obtained by personal visits or telephone calls by the Bureau’s
trained representatives.

In calculating the index, price changes for the various items in each location
are aggregated using weights, which represent their importance in the spending
of the appropriate population group. Local data are then combined to obtain a
U.S. city average. For the CPI-U and CPI-W, separate indexes are also published
by size of city, by region of the country, for cross-classifications of regions
and population-size classes, and for 23 selected local areas. Area indexes do not
measure differences in the level of prices among cities; they only measure the
average change in prices for each area since the base period. For the C-CPI-U,
data are issued only at the national level. The CPI-U and CPI-W are considered
final when released, but the C-CPI-U is issued in preliminary form and subject
to three subsequent quarterly revisions.

The index measures price change from a designed reference date. For most of the
CPI-U and the CPI-W, the reference base is 1982-84 equals 100. The reference
base for the C-CPI-U is December 1999 equals 100.  An increase of 7 percent from
the reference base, for example, is shown as 107.000. Alternatively, that
relationship can also be expressed as the price of a base period market basket
of goods and services rising from $100 to $107. 

Sampling Error in the CPI

The CPI is a statistical estimate that is subject to sampling error because it
is based upon a sample of retail prices and not the complete universe of all
prices. BLS calculates and publishes estimates of the 1-month, 2-month, 6-month,
and 12-month percent change standard errors annually for the CPI-U. These standard
error estimates can be used to construct confidence intervals for hypothesis
testing. For example, the estimated standard error of the 1-month percent change
is 0.03 percent for the U.S. all items CPI. This means that if we repeatedly sample
from the universe of all retail prices using the same methodology, and estimate a
percentage change for each sample, then 95 percent of these estimates will be within
0.06 percent of the 1-month percentage change based on all retail prices. For
example, for a 1-month change of 0.2 percent in the all items CPI-U, we are
95 percent confident that the actual percent change based on all retail prices would
fall between 0.14 and 0.26 percent. For the latest data, including information on
how to use the estimates of standard error, see
https://www.bls.gov/cpi/tables/variance-estimates/home.htm.

Calculating Index Changes

Movements of the indexes from 1 month to another are usually expressed as percent
changes rather than changes in index points, because index point changes are
affected by the level of the index in relation to its base period, while percent
changes are not. The following table shows an example of using index values to
calculate percent changes:

                               Item A                  Item B                      Item C
Year I                         112.500                 225.000                     110.000
Year II                        121.500                 243.000                     128.000
Change in index points         9.000                   18.000                      18.000
Percent change                 9.0/112.500 x 100 = 8.0  18.0/225.000 x 100 = 8.0   18.0/110.000 x 100 = 16.4

Use of Seasonally Adjusted and Unadjusted Data

The Consumer Price Index (CPI) produces both unadjusted and seasonally adjusted data.
Seasonally adjusted data are computed using seasonal factors derived by the X-13ARIMA-
SEATS seasonal adjustment method. These factors are updated each February, and the new
factors are used to revise the previous 5 years of seasonally adjusted data. The
factors are available at
www.bls.gov/cpi/tables/seasonal-adjustment/seasonal-factors-2021.xlsx. For more
information on data revision scheduling, please see the Factsheet on Seasonal
Adjustment at www.bls.gov/cpi/seasonal-adjustment/questions-and-answers.htm and
the Timeline of Seasonal Adjustment Methodological Changes at
www.bls.gov/cpi/seasonal-adjustment/timeline-seasonal-adjustment-methodology-changes.htm.

For analyzing short-term price trends in the economy, seasonally adjusted changes are
usually preferred since they eliminate the effect of changes that normally occur at
the same time and in about the same magnitude every year—such as price movements
resulting from weather events, production cycles, model changeovers, holidays, and
sales. This allows data users to focus on changes that are not typical for the time
of year. The unadjusted data are of primary interest to consumers concerned about
the prices they actually pay. Unadjusted data are also used extensively for escalation
purposes. Many collective bargaining contract agreements and pension plans, for example,
tie compensation changes to the Consumer Price Index before adjustment for seasonal
variation. BLS advises against the use of seasonally adjusted data in escalation
agreements because seasonally adjusted series are revised annually.

Intervention Analysis

The Bureau of Labor Statistics uses intervention analysis seasonal adjustment for some
CPI series. Sometimes extreme values or sharp movements can distort the underlying
seasonal pattern of price change. Intervention analysis seasonal adjustment is a process
by which the distortions caused by such unusual events are estimated and removed from
the data prior to calculation of seasonal factors. The resulting seasonal factors, which
more accurately represent the seasonal pattern, are then applied to the unadjusted data.

For example, this procedure was used for the motor fuel series to offset the effects of
the 2009 return to normal pricing after the worldwide economic downturn in 2008.
Retaining this outlier data during seasonal factor calculation would distort the
computation of the seasonal portion of the time series data for motor fuel, so it was
estimated and removed from the data prior to seasonal adjustment. Following that,
seasonal factors were calculated based on this “prior adjusted” data. These seasonal
factors represent a clearer picture of the seasonal pattern in the data. The last step
is for motor fuel seasonal factors to be applied to the unadjusted data.

For the seasonal factors introduced for January 2021, BLS adjusted 72 series using
intervention analysis seasonal adjustment, including selected food and beverage items,
motor fuels, electricity, and vehicles.

Revision of Seasonally Adjusted Indexes

Seasonally adjusted data, including the U.S. city average all items index levels, are
subject to revision for up to 5 years after their original release. Every year, economists
in the CPI calculate new seasonal factors for seasonally adjusted series and apply them to
the last 5 years of data. Seasonally adjusted indexes beyond the last 5 years of data are
considered to be final and not subject to revision. For January 2021, revised seasonal
factors and seasonally adjusted indexes for 2016 to 2020 were calculated and published.
For series which are directly adjusted using the Census X-13ARIMA-SEATS seasonal adjustment
software, the seasonal factors for 2020 will be applied to data for 2021 to produce the
seasonally adjusted 2021 indexes. Series which are indirectly seasonally adjusted by
summing seasonally adjusted component series have seasonal factors which are derived and
are therefore not available in advance.

Determining Seasonal Status

Each year the seasonal status of every series is reevaluated based upon certain statistical
criteria. Using these criteria, BLS economists determine whether a series should change its
status from "not seasonally adjusted" to "seasonally adjusted", or vice versa. If any of
the 81 components of the U.S. city average all items index change their seasonal adjustment
status from seasonally adjusted to not seasonally adjusted, not seasonally adjusted data
will be used in the aggregation of the dependent series for the last 5 years, but the
seasonally adjusted indexes before that period will not be changed. Thirty-four of the
81 components of the U.S. city average all items index are not seasonally adjusted for 2021.

Contact Information

For additional information about the CPI visit www.bls.gov/cpi or contact the CPI
Information and Analysis Section at 202-691-7000 or cpi_info@bls.gov.

For additional information on seasonal adjustment in the CPI visit
www.bls.gov/cpi/seasonal-adjustment/home.htm or contact the CPI seasonal adjustment section
at 202-691-6968 or cpiseas@bls.gov.

Information from this release will be made available to sensory impaired individuals upon
request. Voice phone: 202-691-5200; Federal Relay Service: 1-800-877-8339. 



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Last Modified Date: October 13, 2021