In maintaining a historical time series of real estate stock, the industry standard approach is to calculate past quarters' stock levels by subtracting buildings from the current level according to their ages. We call this calculated stock. This measure doesn't account for buildings that were demolished, however, so historical stock is always underestimated to some degree. To see if we can address this, we are working to develop a “gross” stock series that adds demolished buildings to the calculated stock measure for the times they were active. The two series are compared in the chart below. Based on available data, retail demolitions average about 0.4% of the total stock each quarter, but because a consistent method of tracking demolitions is not in place, we think this figure is low. (But we'll keep trying.)
Historical Retail Stock Series: Calculated vs. Gross
Source: CBRE Econometric Advisors, Q2 2017.