Keeping Comparisons Relevant with CSS Index Data

Stats Deep Dive

For over 50 years, NFPA manufacturer members have contributed monthly data to the  Confidential Shipment Statistics (CSS) program to get the aggregated industry results for tracking the latest market trends in pneumatic, industrial hydraulic, and mobile hydraulic products. That same market data also offers insights into your own company’s performance against the rest of the industry. While the CSS program reports market data in both dollar and index formats, index data plays a much larger role. To get the full benefit of the data, users should understand why index data plays such an important role in participation-based data reports, how comparable index data is to dollar data, and how easily CSS index data fits into your company’s strategic planning.

Why Indexes?
Indexes help keep data comparable and minimize the effect of changes in participation from one time period to the next for more accurate trend analysis. Dollar data is not comparable from one time period to the next if changes in participation occur.

CSS Index

The formula to calculate an index is (Current $ / Base Year $)*100.

For example, the index for total pneumatic filter shipments in month 1 above is calculated as follows: (4,089,134 / 2,815,550)*100 = 145.2

CSS Index Data

Calculations of percent change provide identical results when all participants report data throughout the selected time period, as we see in the percent changes from month 1 and month 2 above.

CSS Index Data

The importance of index data becomes very clear when we compare the percent changes of month 1 and a revised month 2 above. Company D did not report data in revised month 2 and created an artificial decrease in the revised month 2 dollar total. Therefore, we can’t compare changes in the dollar totals from month 1 to revised month 2. But we can still make relevant comparisons between the two months by using index data. The change in participation has minimal effect because the calculation of the total index accounts for Company D’s missing current data by removing Company D’s base year data.

While index data is extremely useful, it is not perfect. Some participating companies can have a greater impact on index data due to the company’s stronger representation (i.e.  larger dollar amount reported) for any given category. Therefore, NFPA maintains a “Top 30 List,” or a list of 30 participants that represent sizable amounts in any given CSS category and are required to submit data every month. When a participating company on the “Top 30 List” is late with submitting their data, NFPA will delay the tabulation of data and reports until the missing data arrives. The “Top 30 List” is confidential and only viewable by NFPA staff.

Next Week, we explore some popular types of analysis using index data.

Questions? Want more information about how to participate in NFPA’s Confidential Shipment Statistics (CSS) program? Please contact Eric Armstrong at or (414) 778-3372.