BAUMOL:UNBALANCED GROWTH 425 the city are usually the very persons who care and can afford to care the ones who maintain their houses,who do not commit crimes,and who are most capable of providing the taxes needed to arrest the process of urban decay.Their exodus therefore leads to further deterioration in urban conditions and so induces yet another wave of emigration,and so on.2 It is clear that these cumulative processes can greatly increase the financial pressur es bese ways:they can increase dire ty and in a va tly municipal costs ing to the real quantities of inputs required for the upkeep of buildings,to maintain levels of urban sanitation,to preserve the level of education attained by an average resident,etc.;they can reduce the tax base-the exodus of more affluent urban inhabitants cause a decline in the financial resources available to the city;and with the passage of time the magnitude of the es to arrest and r the cumulative pro s itself s likely to grow so that the city may find it easingly difficult to go beyond programs that slow the processes slightly. As is to be epcted,such dynamic p ,stable ding maybe inherently d f (lagged public transport supply response) so that f4=o十am+j :Lh the coefficient tb is presumanye of automotive traffic,the corresponding relation- Da'+'A and D(delays today lead to lower trafic tomorrow) so that we have a negative coeficientin the difference equation A+=u一a-bA. n in service let tostill another fall in the la totally unacceptabl as a matter of public policy. ed hcarepedkeihodi rmation betwe n by an mo Copyright2001 All Rights Reserved