When a city experiences a sharp decline in population, the city' s tax revenues, which pay for such city services as police protection and maintenance of water lines, also decrease  The area to be policed and the number and length of the water lines to be maintained, however, do not decrease
Attempting to make up the tax revenue lost by raising tax rates is not feasible, since higher tax rates would cause even more residents to leave
If, in a city with sharply declining population, police protection and water line maintenance do not deteriorate, some other service previously provided by the city will deteriorate or be eliminated.