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NYC 9/11 Public Portal Document

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floor space at equilibrium. In the case of the housing market, the utilization rate takes the form of vacant housing units at equilibrium which is directly measurable by data on vacant units. In the case of the commercial market, the underutilization rate is implicit and an explicit vacancy rate cannot be generated, since vacancy information are not uniformly available for commercial floor space.

The Model Formulation In the following presentation of the equilibrium set of equations, the basic notation used to define the dimensions of household choices are first described. Lower case letters stand for subscripts, while upper case letters stand for the highest values the subscripts can obtain.

i = 1...I: denotes an employment zone (i.e., a zone in which some employment is located). j = denotes a residential zone (i.e., a zone in which some housing is available). k = 1...K: denotes the housing types which are available in the residential zone j. m = denotes the modes of travel available for commuting between a zone of residence j and a zone of employment i. 1 1...L: denotes a shopping zone where commercial real estate provides shopping opportunities.

n = 1...N: denotes the modes of travel available for shopping between every residential zone j and shopping zone 1.

It will be convenient to refer more briefly to the triplet (j,k,m) as *'a residential choice" and to the pair (l,n) as "a shopping choice". For clarity in exposition, we will present the model equations by assuming that the household has only one working member. Subsequently, we will make adaptations to deal approximately with the presence of multiple workers per household. The utility of the household is specified as follows for each jkm;i:

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