Producer Price Index (PPI)
|
Index Point Change | |
---|---|
Finished Goods Price Index | 107.5 |
Less previous index | 104.0 |
Equals index point change | 3.5 |
Percent Change | |
---|---|
Index point difference | 3.5 |
Divided by the previous index | 104.0 |
Equals | 0.034 |
Results multiplied by one hundred | 0.034 x 100 |
Equals percent change | 3.4 |
Because price data are used for different purposes by different groups, BLS publishes seasonally adjusted and unadjusted changes each month. Seasonally adjusted data are preferred for analyzing general price trends in the economy, because these data eliminate the effect of changes that normally occur at about the same time, and in about the same magnitude, every year-such as price movements resulting from normal weather patterns, regular production and marketing cycles, model changeovers, seasonal discounts, and holidays. For these reasons, seasonally adjusted data more clearly reveal underlying cyclical trends. Unadjusted data are of primary interest to users who need information that can be related to actual dollar values of transactions. Individuals requiring this information include marketing specialists, purchasing agents, budget and cost analysts, contract specialists, and commodity traders. It is the unadjusted data that are generally cited in escalating long-term contracts such as purchasing agreements or real estate leases. (See Escalation and Producer Price Indexes: A Guide for Contracting Parties, BLS Report 807, September 1991, available on request from the BLS.)
In 1998, the PPI implemented the X-12-ARIMA Seasonal Adjustment Method; prior to that year the PPI employed the X-11 method. Each year, the seasonal status of most commodity indexes is re-evaluated to reflect more recent price behavior. Industry net output indexes are not seasonally adjusted. For time series that exhibit seasonal pricing patterns, new seasonal factors are estimated and applied to the unadjusted data for the previous 5 years. These updated seasonally adjusted indexes replace the most recent 5 years of seasonal data.
Seasonal factors may be applied to series using either a direct or aggregative method. Generally, commodity indexes are seasonally adjusted using direct seasonal adjustment, which produces a more complete elimination of seasonal movements than the aggregative method. However, the direct seasonal adjustment process may not yield figures that possess additive consistency. Thus, a seasonally adjusted index for a broad category that is directly adjusted may not be logically consistent with all seasonally adjusted indexes for its components. Seasonal movements for stage-of-processing indexes are derived indirectly through an aggregative method that combines movements of a wide variety of subproduct class (6- digit) series.
Seasonally adjusted indexes can become problematic when previously stable and predictable price patterns abruptly change. If the new pattern persists, the seasonal adjustment method will eventually reflect it adequately; if these patterns keep shifting, however, seasonally adjusted data will become chronically troublesome. This problem occurs relatively infrequently for farm and food-related products but has more often affected manufactured products such as automobiles and steel.
Since January 1988, the PPI has used Intervention Analysis Seasonal Adjustment methods to enhance the calculation of seasonal factors. With this technique, outlier values that may distort the seasonal pattern are removed from the data prior to applying the standard seasonal factor estimation procedure. For example, a possible economic cause for large price movements for petroleum-based products might have been the Persian Gulf War. In this case, intervention techniques allowed for better estimates of seasonally adjusted data. On the whole, very few series have required intervention. Out of nearly 900 seasonally adjusted series, only 16 interventions were performed in 1997.
For more information relating to seasonal adjustment methods, see (1)
"Appendix A: Seasonal Adjustment Methodology at BLS," in the BLS Handbook
of Methods (April 1997), Bulletin 2490 and (2) "Summary of Changes to the
PPI's Seasonal Adjustment Methodology" in the January 1995 issue of
Producer Price Indexes.
PPI data can be obtained from the WWW address (http://www.bls.gov/ppi). Scrolling down the page to the "Get Detailed Statistics" header reveals the following 5 methods of data retrieval:
Most Requested Series is a form-based application that allows the user to quickly obtain PPI time series data by selecting from two separate lists (commodity and industry) of the most commonly requested time series, including the All Commodities Index and the stage-of-processing indexes (for example, Finished Goods). Within each list, any one-or all-of the time series shown can be selected. A user can modify the date range and output options after executing the query, using the reformat button above the data output table.
Create Customized Tables is a form-based query application designed for users unfamiliar with the PPI coding structure. It guides a user through the PPI classification system by listing index titles and does not require knowledge of commodity or industry codes. Data retrieved are based on a query formulated by selecting data characteristics from lists provided. Two options are available to create customized tables, depending on a user's browser capability. The one-screen option is a Java application that uses a single screen to guide a user through the available time series data. The second option is a multiple screen, nonJava-based application. Both methods allow a user to browse the PPI coding structure and select multiple series codes. Using the one-screen option, users can modify the date range and output options after executing the query using the reformat button above the data output table.
Series Report is a form-based application that uses formatted PPI time series identifiers (commodity or industry codes) as input in extracting data according to a specified set of date ranges and output options. This application provides the most efficient path for those users who are familiar with the format of PPI time series identifiers. Up to 300 indexes can be extracted at one time.
There are three basic formats for creating a unique PPI time series identifier. For commodity and stage-of-processing indexes, enter a "wpu" prefix (not seasonally adjusted) or a "wps" prefix (seasonally adjusted) in combination with a commodity-based code to create a series identifier.
Commodity code |
Will provide data for: |
---|---|
wps063 | Drugs and pharmaceuticals, seasonally adjusted |
wpu063803 | Pharmaceutical preparations, cardiovascular system |
wpusop3000 | Finished goods, not seasonally adjusted |
For a current industry-based price index organized according to the North American Industry Classification System (NAICS), enter the prefix "pcu" followed by the industry-product code. The series identifier for products primary to an industry include 12 numeric digits, the six-digit industry code is repeated, and up to seven additional digits of product detail. Dashes are used as place holders for higher-level industry group codes.
Industry-product code, current NAICS series |
Will provide data for: |
---|---|
pcu325---325--- | Chemical manufacturing, not seasonally adjusted |
pcu336110336110 | Automobile and light duty motor vehicle manufacturing |
pcu621111621111411 | Offices of physicians, one and two physician practices and single specialty group practices, general/family practices |
To identify a discontinued industry-product code based on the Standard Industrial Classification (SIC), enter a "pdu" prefix and "#" between the fourth and fifth characters of the product code. A series identifier for the discontinued dataset uses underscores as placeholders to complete a reference to an SIC industry group code of less than four digits. (All PPI industry-based indexes organized by SIC were discontinued with the introduction of the NAICS.) In all cases, no spaces are permitted.
Industry-product code, discontinued SIC series |
Will provide data for: |
---|---|
pdu28__# | Chemicals and allied products, not seasonally adjusted |
pdu331_# | Blast furnaces, steel works, and rolling and finishing mills, not seasonally adjusted |
pdu3711#111 | Passenger cars |
Flat Files and the FTP server are best suited for those users requiring access to either a large volume of time series data or other PPI-related documentation (such as, seasonal factor and relative importance tables). The FTP site can be accessed at (ftp://ftp.bls.gov) or directly from the links on the "Get Detailed Statistics" page or the PPI homepage. Data and documentation available for download include:
Data/Documentation |
Directory: |
---|---|
NAICS Current Series | /pub/time.series/pc |
SIC Discontinued Series | /pub/time.series/pd |
Commodity Series | /pub/time.series/wp |
Special Requests | /pub/special.requests/ppi |
Latest News Release | /pub/news.release/ppi.txt |
The FTP site maintains files to help with searches and downloads. These files are centrally located in the /pub/doc directory. Within this directory, go to the overview.txt file for an overview relating to all BLS data available through the FTP site. For commodity-based PPI data (which appear in tables 1, 2, 3, 6, 7, and 8 of the PPI monthly detailed report and tables 1, 2, 3, and 5 of the monthly news release), the program help file is wp.txt. For current industry-based PPI data based on the NAICS (which appear in tables 4, 5, and 9 of the monthly PPI report and table 4 of the monthly news release), the file is pc.txt. For industry-based SIC time series that have been discontinued, go to pd.txt. (These and other help files are also maintained within each of the five directories listed above.)
PPI data can also be accessed via the BLS homepage (http://www.bls.gov). After clicking the "Get Detailed Statistics" link at the top of the homepage a chart appears listing all of the available BLS programs. The following four methods are available for PPI data: Most requested statistics, create customized tables (one screen or multiple screens), and flat files. Additional sources of BLS data are also accessible from this page including: Economic news releases, series report, and economy at a glance.
The PPI homepage (http://www.bls.gov/ppi) contains additional information regarding PPI data and methodology. The top section of the homepage provides PPI news releases, both current and archived, as well as general PPI information. The "Tables Created by BLS" section found beneath the statistics section provides relative importance and seasonal factor tables. The remaining sections offer special notices and publications pertaining to PPI methodology and applications.
Last Modified Date: May 16, 2008
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