7%; site improvement costs, 8%; labour costs, 27%; materials costs, 33%; finance costs, 3%; administrative costs, 17%; and marketing costs, 5%. Public-subdivision requirements can increase development costs by up to 3%, depending on the jurisdiction. Differences in building codes account for about a 2% variation in development costs. However, these subdivision and building-code costs typically increase the market value of the buildings by at least the amount of their cost outlays. A production function such as can be constructed in which is the quantity of houses produced, is the amount of labour employed, is the amount of land used, and is the amount of other materials. This production function must, however, be adjusted to account for the refurbishing and augmentation of existing buildings. To do this, a second production function is constructed that includes the stock of existing housing and their ages as determinants. The two functions are summed, yielding the total production function. Alternatively, a hedonic pricing model can be regressed. The long-run price elasticity of supply is quite high. George Fallis (1985) estimates it as 8.2, but in the short run, supply tends to be very price-inelastic. Supply-price elasticity depends on the elasticity of substitution and supply restrictions. There is significant substitutability, both between land and materials and between labour and materials. In high-value locations, developers can typically construct multi-story concrete buildings to reduce the amount of expensive land used. As labour costs have increased since the 1950s, new materials and capital-intensive techniques have been employed to reduce the amount of labour used. However, supply restrictions can significantly affect substitutability. In particular, the lack of supply of skilled labour (and labour-union requirements) can constrain the substitution from capital to labour. Land availability can also constrain substitutability if the area of interest is delineated (i.e., the larger the area, the more suppliers of land, and the more substitution that is possible). Land-use controls such as zoning bylaws can also reduce land substitutability. Adjustment mechanism The basic adjustment mechanism is a stock/flow model to reflect the fact that about 98% the market is existing stock and about 2% is the flow of new buildings. In the adjacent diagram, the stock of housing supply is presented in the left panel while the new flow is in the right panel. There are four steps in the basic adjustment mechanism. First, the initial equilibrium price (Ro) is determined by the intersection of the