As provided by the Census, start occurs when excavation begins for the footings or foundation of a building. All housing units in a multifamily building are defined as being started when this excavation begins. Beginning with data for September 1992, estimates of housing starts include units in structures being totally rebuilt on an existing foundation.
In interpreting changes in the statistics in this release, note that month‐to‐month changes in seasonally adjusted statistics often show movements which may be irregular. It may take three months to establish an underlying trend for building permit authorizations, six months for total starts, and six months for total completions. The statistics in this release are estimated from sample surveys and are subject to sampling variability as well as nonsampling error including bias and variance from response, nonreporting, and undercoverage.