In interpreting Table 4, the reader is cautioned, however, that there may be an
endogeneity problem with the bus service frequency variable. As Holmgren (2007)
points out, variables reflecting the extent of PT service actually may be partly
endogenous, since public transport providers gear service levels to ridership.
Unfortunately, since there currently exist no econometric technique for testing
and adjusting for endogeneity within the context of a cross-sectional spatial errors
regression model, no such tests or adjustments are undertaken here, and the
reader is left with a warning about this potential problem