Commercial Buildings Trend—Detail
 
Commercial Floorspace Trend—Detail
 

Adjustments to CBECS Data

The first survey of energy consumption in commercial buildings, conducted in 1979, was the first national-level survey of commercial buildings (rather than establishments) of any kind. (The survey was called the Nonresidential Buildings Energy Consumption Survey or NBECS from 1979 to 1986.) In 1979 and 1983, EIA selected the building sample from a previously existing frame of commercial buildings that was developed for other purposes. In 1986, a new frame was developed specifically for NBECS, based on multistage area probability methods. (See “Technical Information on CBECS” on the CBECS Home Page for complete details of survey methodology.)

When EIA analyzed the 1986 NBECS data it discovered that the data were not consistent with those collected in the 1979 and 1983 NBECS—there was an apparent undercount of commercial buildings in the 1979 survey (and 1983 since it used the 1979 frame). In the 1986 CBECS (and in subsequent CBECS) the estimate of buildings constructed in 1979 or earlier was larger than estimated in either the 1979 or 1983 NBECS (i.e., there was an increase in “old” buildings). EIA concluded that the 1979 sample frame was deficient and that the 1979 and 1983 NBECS underestimated the commercial building population.

To analyze trends in CBECS data for this series of reports, the 1979 and 1983 NBECS data were adjusted to account for the undercount of buildings. The estimates of total buildings (and floorspace of buildings) constructed in 1979 or earlier are consistent in the 1986, 1989, and 1992 CBECS and are assumed to be better estimates of buildings and floorspace than totals from the 1979 NBECS. The 1983 NBECS data were adjusted in a similar manner, using buildings constructed in 1983 or earlier.

Change in Definition of Target Population of Commercial Buildings in 1995 CBECS
 

In 1995, EIA changed the the way that the target population of commercial buildings was defined for the CBECS. Two types of buildings included in previous surveys, were excluded. Those building types were parking garages, and commercial buildings located on multibuilding manufacturing facilities. Sufficient information was collected in the 1989 and 1992 CBECS so that those data can be adjusted to match the 1995 definition. The adjustments allow these three surveys to be compared directly. Earlier CBECS did not collect enough information about the manufacturing facilities to permit those data to be adjusted.

Release date: 01/12/2000

http://www.eia.doe.gov/emeu/consumptionbriefs/cbecs/cbecs_trends/adjustment.html

If you are having any technical problems with this site, please contact the EIA webmaster at wmaster@eia.doe.gov.