Consumer Price Index Summary

Transmission of material in this release is embargoed until                                        
8:30 a.m. (EDT) May 10, 2018   		       USDL-18-0744

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

CONSUMER PRICE INDEX – APRIL 2018

The Consumer Price Index for All Urban Consumers (CPI-U) increased 0.2 percent in
April on a seasonally adjusted basis after falling 0.1 percent in March, the U.S.
Bureau of Labor Statistics reported today. Over the last 12 months, the all items
index rose 2.5 percent before seasonal adjustment.

The indexes for gasoline and shelter were the largest factors in the seasonally
adjusted increase in the all items index, although the food index increased as well.
The gasoline index increased 3.0 percent, more than offsetting declines in other
energy component indexes and led to a 1.4-percent rise in the energy index. The
food index rose 0.3 percent, with the food at home index rising 0.3 percent and the
index for food away from home increasing 0.2 percent. 

The index for all items less food and energy rose 0.1 percent in April. The shelter
index rose 0.3 percent, with other indexes mixed. The indexes for household
furnishings and operations, personal care, tobacco, medical care, and apparel all
increased in April, while those for used cars and trucks, new vehicles, recreation,
and airline fares all declined.  
 
The all items index rose 2.5 percent for the 12 months ending April; this figure
has been mostly trending upward since it was 1.6 percent for the period ending June
2017. The index for all items less food and energy rose 2.1 percent for the 12
months ending April. The food index increased 1.4 percent, and the energy index
rose 7.9 percent. 


 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.
                              Oct.  Nov.  Dec.  Jan.  Feb.  Mar.  Apr.   ended 
                              2017  2017  2017  2018  2018  2018  2018   Apr.  
                                                                         2018  
                                                                               
                                                                               
 All items..................    .1    .3    .2    .5    .2   -.1    .2      2.5
  Food......................    .1    .0    .2    .2    .0    .1    .3      1.4
   Food at home.............    .1   -.1    .2    .1   -.2    .1    .3       .5
   Food away from home (1)..    .1    .2    .2    .4    .2    .1    .2      2.5
  Energy....................  -1.4   3.2   -.2   3.0    .1  -2.8   1.4      7.9
   Energy commodities.......  -3.0   5.8   -.7   5.8   -.9  -4.7   3.0     13.7
    Gasoline (all types)....  -3.2   6.0   -.8   5.7   -.9  -4.9   3.0     13.4
    Fuel oil................   1.4   5.6    .9   9.5  -3.6   -.7   2.7     22.6
   Energy services..........    .4    .5    .4   -.8   1.4   -.2   -.5      1.2
    Electricity.............    .4    .5    .2   -.2    .4    .0   -.6      1.2
    Utility (piped) gas                                                        
       service..............    .4    .7   1.0  -2.6   4.7  -1.2   -.4      1.0
  All items less food and                                                      
     energy.................    .2    .1    .2    .3    .2    .2    .1      2.1
   Commodities less food and                                                   
      energy commodities....    .0   -.1    .2    .4    .1   -.1   -.1      -.4
    New vehicles............   -.2    .2    .5   -.1   -.5    .0   -.5     -1.6
    Used cars and trucks....    .7    .5    .7    .4   -.3   -.3  -1.6      -.9
    Apparel.................   -.2   -.9   -.3   1.7   1.5   -.6    .3       .8
    Medical care commodities    .0    .5    .9   -.1   -.3    .1   -.2      1.9
   Services less energy                                                        
      services..............    .3    .2    .3    .3    .2    .3    .2      2.9
    Shelter.................    .3    .2    .3    .2    .2    .4    .3      3.4
    Transportation services     .4    .1    .3    .8   1.0    .2   -.4      4.1
    Medical care services...    .3   -.1    .2    .6    .0    .5    .2      2.2

   1 Not seasonally adjusted.

Food

The food index rose 0.3 percent in April after a 0.1-percent increase in March. The
index for food at home rose 0.3 percent, the largest increase since March 2017. The
fruits and vegetables index rose 1.0 percent in April after declining in February
and March. The index for meats, poultry, fish, and eggs increased 0.7 percent, with
the index for eggs rising 7.1 percent and the beef index rising 1.3 percent. The
index for dairy and related products also increased in April, rising 0.4 percent. 

In contrast, the index for nonalcoholic beverages fell 0.6 percent in April after
rising in March. The index for cereals and bakery products fell 0.2 percent in
April, and the index for other food at home was unchanged. The index for food away
from home rose 0.2 percent in April following a 0.1-percent increase in March.

Over the last 12 months, the index for food away from home increased 2.5 percent,
and the food at home index rose 0.5 percent. The index for meats, poultry, fish,
and eggs increased 3.5 percent over the last year, the only one of the six major
grocery store food group indexes to increase. The indexes for cereals and bakery
products and for other food at home were unchanged, and the remaining indexes
declined modestly over the last 12 months. 

Energy

The energy index rose 1.4 percent in April after falling 2.8 percent in March. The
gasoline index rose 3.0 percent following a 4.9-percent decline in March. (Before
seasonal adjustment, gasoline prices increased 6.2 percent in April.) In contrast,
the electricity index fell 0.6 percent in April, and the index for natural gas fell
0.4 percent.  

The energy index increased 7.9 percent over the past year, with all the major
component indexes rising. The gasoline index increased 13.4 percent and the fuel oil
index rose 22.6 percent. The remaining component indexes increased more moderately;
the electricity index increased 1.2 percent, and the index for natural gas advanced
1.0 percent.   

All items less food and energy

The index for all items less food and energy increased 0.1 percent in April. The
shelter index increased 0.3 percent, with the rent index rising 0.4 percent and the
index for owners' equivalent rent increasing 0.3 percent. The index for lodging
away from home increased 0.7 percent in April. The index for household furnishings
and operations rose 0.5 percent in April, the largest increase since April 2015,
and the personal care index increased 0.7 percent.

The apparel index rose 0.3 percent in April after declining in March, and the
tobacco index increased 1.3 percent. The medical care index rose 0.1 percent in
April, with the hospital services index rising 0.2 percent, the prescription drugs
index increasing 0.1 percent, and the physicians' services index unchanged. The
indexes for education and for alcoholic beverages also rose in April.

The index for used cars and trucks fell 1.6 percent in April, the largest decline
since March 2009. The recreation index fell 0.4 percent, the largest decline since
December 2009. The index for airline fares fell 2.7 percent in April, and the new
vehicles index declined 0.5 percent. The index for motor vehicle insurance fell 0.2
percent, the first monthly decline since April 2017. The index for communication
also declined 0.2 percent in April.

The index for all items less food and energy rose 2.1 percent over the past 12
months, the same increase as for the period ending March. The shelter index rose
3.4 percent over the last 12 months, and the medical care index rose 2.2 percent.
Indexes that declined over the past 12 months include those for new vehicles,
airline fares, used cars and trucks, and communication.

Not seasonally adjusted CPI measures

The Consumer Price Index for All Urban Consumers (CPI-U) increased 2.5 percent over
the last 12 months to an index level of 250.546 (1982-84=100). For the month, the
index increased 0.4 percent prior to seasonal adjustment.  

The Consumer Price Index for Urban Wage Earners and Clerical Workers (CPI-W)
increased 2.6 percent over the last 12 months to an index level of 244.607 
1982-84=100). For the month, the index increased 0.5 percent prior to seasonal 
adjustment.  

The Chained Consumer Price Index for All Urban Consumers (C-CPI-U) increased 2.3
percent over the last 12 months. For the month, the index increased 0.4 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 May 2018 is scheduled to be released on Tuesday, 
June 12, 2018, at 8:30 a.m. (EDT).


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 5,000 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. 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 in January 2018, BLS adjusted 38 series using intervention analysis
seasonal adjustment, including selected food and beverage items, motor fuels, and natural gas.

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. In
January 2018, revised seasonal factors and seasonally adjusted indexes for 2013 to 2017 were calculated
and published. For series which are directly adjusted using the Census X-13ARIMA-SEATS seasonal adjustment
software, the seasonal factors for 2017 will be applied to data for 2018 to produce the seasonally
adjusted 2018 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.
Twenty-nine of the 81 components of the U.S. city average all items index are not seasonally adjusted
for 2018.

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
https://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: May 10, 2018