Readers of ENR direct a steady stream of questions about the magazine’s indexes and how to accurately apply them to various construction projects. To help clarify the nature and uses of the cost indexes, here are answers to the most frequently asked questions and suggestions on how to avoid costly mistakes.

What is the difference between ENR’s Construction Cost Index and its Building Cost Index?
The difference is in their labor component. The CCI uses 200 hours of common labor, multiplied by the 20-city average rate for wages and fringe benefits. The BCI uses 68.38 hours of skilled labor, multiplied by the 20-city wage- fringe average for three trades–bricklayers, carpenters and structural ironworkers. For their materials component, both indexes use 25 cwt of fabricated standard structural steel at the 20-city average price, 1.128 tons of bulk portland cement priced locally and 1,088 board ft of 2x4 lumber priced locally. The ENR indexes measure how much it costs to purchase this hypothetical package of goods compared to what it was in the base year.

What kinds of construction do the ENR indexes represent?
The two indexes apply to general construction costs. The CCI can be used where labor costs are a high proportion of total costs. The BCI is more applicable for structures.

Where does ENR get its data?
ENR has price reporters covering 20 U.S. cities who check prices locally. The prices are quoted from the same suppliers each month. ENR computes its latest indexes from these figures and local union wage rates.

Does ENR have cost indexes for cities outside the U.S.?
No. However, we publish a limited amount of international cost data in our Fourth Quarterly Cost Report in December.

Are material prices averaged?
No. ENR reporters collect "spot prices" from a single source for all of the materials tracked, including those in the index. The reporters survey the same suppliers each month for materials that affect the index. Actual prices within a city may vary depending on the competitiveness of the market and local discounting practices. This method allows for a quick indicator of price movement, which is its primary objective.

Do the city indexes have different weightings?
No. Each city uses the same weight for the labor and materials components as the U.S. average index.

Do the indexes measure cost differentials between cities?
No. This is one of the more common errors in the application of ENR’s indexes, which only measure the trend in an individual city and in the U.S. as a whole. Differentials between cities may reflect differences in labor productivity and building codes. Moreover, quoting bases for lumber and cement vary from one city to another. One city may report list prices while in another prices for the same material may include discounts.

Are indexes seasonally adjusted?
No. This is an important point for users of the indexes to keep in mind. Wages, the most important component, usually affect the indexes once or twice a year. Cement prices tend to be more active in the spring while fabricated structural steel pricing tends to have monthly adjustments. Lumber prices, more dependent on local pricing and production conditions, are the most volatile and can change appreciably from month to month. Declines in indexes are most often the result of falling lumber prices.

The study of an index movement for a period of less than 12 months can sometimes miss these important developments. Users of an index for individual cities should also watch the timing of wage settlements. Stalled labor negotiations may keep the old wage rate in effect longer than a 12-month period, giving the appearance of a low inflation rate.

Is it more accurate to use an index that is closest to my home city?
No. The 20-city average index is generally more appropriate. Because it has more elements, it has a smoother trend. Indexes for individual cities are more susceptible to price spikes.

Are annual averages weighted?
No. They are straight mathematical averages.

How are the indexes calculated?
ENR’s national indexes are updated in the first week of each month on the Construction Economics pages of the magazine while indexes for individual cities appear in the second issue of the month. Prices for the indexes’ materials component are published in the preceding month on the Construction Economics pages. Cement prices are in the first issue of the month, lumber prices in the third and steel in the fourth issue. National average wage rates are published in the third Quarterly Cost Report.

The index was designed as a general-purpose construction cost index that would measure the basic groundswells in construction costs. It is a weighted aggregative index with a fixed base, made up of select quantities of construction materials and labor, multiplied by their actual prices. It was constructed so that its base is a hypothetical block of construction that cost $100 in 1913. Calculations include proprietary factors developed and tested by ENR economists over the last 100 years. Indexes cannot be self-calculated by the reader.

Does ENR forecast its indexes?
Yes. ENR projects its BCI and CCI for the next 12 months once a year in the Fourth Quarterly Cost Report. To reach its forecast, ENR incorporates the new wage rates called for in multiyear, collective-bargaining agreements and estimates for areas where new contract terms will be negotiated. ENR estimates the materials component by studying consumption forecasts and price trends.

Does ENR ever change the weighting of the index components?
No. The components are always multiplied by the same factors. However, a component’s share of an index’s total will shift with its relative escalation rate.

Has ENR ever changed the makeup of the index components?
Yes. Only once, in 1996. ENR was forced to switch from the mill price for structural steel to the 20-city average fabricated price for channel beams, I-beams and wide-flanges when ENR’s sources for mill prices left the structural market.

Does ENR revise the indexes?
Yes. On some occasions, ENR must revise the indexes. For example, ENR revised its March 2004 indexes shortly after their initial publication to reflect the huge surcharges being placed on structural steel. Revisions to national indexes are published below. Revisions to indexes for individual cities are published in the tables on the following pages.

Do ENR's cost indexes capture all the factors influencing construction costs?
No. ENR's two primary cost indexes, the Construction Cost Index and the Building Cost Index, each have only four components (inputs) -- cement, lumber, structural steel, and labor. They do not capture all the factors influencing project costs. They merely offer a snapshot of general cost trends.

Why doesn't ENR publish data on construction costs in Florida or Arizona?
When we first began collecting cost data in the 1930's Florida and Arizona were very lightly populated. We have decided not to revise our list of 20 cities, in order to preserve the continuity of our data sets.

Where can I obtain data on construction costs in Florida or Arizona, or other states that ENR does not collect cost data from?
There are three major firms that collect construction cost data -- R.S. Means, Marshall and Swift/Boeckh, and BNI Books -- all of which have data for most regions of the U.S., including Florida and Arizona.

What data does ENR publish on building material prices?
ENR has been collecting, compiling and publishing price data on 66 different building materials, in 20 major U.S. cities, on a monthly basis for over 50 years. We publish a table of cement and concrete and aggregate prices in our first weekly issue every month, pipe prices the second week, lumber, drywall and insulation prices the third week, and steel prices the fourth week.

How can I get any of this building material price data going back in time?
If you only need this data for a few specific months in the past, the best way to get it is to get those tables off our website. The monthly tables since January 2005 are posted on our website. To find them, go to our Construction Economics Index. 

If you need cost data prior to 2005, then you need to find a library that has copies of ENR for that time period.

If you have any further questions, please call ENR Economics Editor Alisa Zevin, phone: 646-849-7117, or email: zevina@enr.com