Test of two hypotheses explaining the size of populations in a system of cities |
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Authors: | Nikolay K. Vitanov |
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Affiliation: | Institute of Mechanics, Bulg. Acad. Sciences, Acad. G. Bonchev Str., Bl. 4, BG-1113 Sofia, Bulgaria |
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Abstract: | Two classical hypotheses are examined about the population growth in a system of cities: Hypothesis 1 pertains to Gibrat's and Zipf's theory which states that the city growth–decay process is size independent; Hypothesis 2 pertains to the so-called Yule process which states that the growth of populations in cities happens when (i) the distribution of the city population initial size obeys a log-normal function, (ii) the growth of the settlements follows a stochastic process. The basis for the test is some official data on Bulgarian cities at various times. This system was chosen because (i) Bulgaria is a country for which one does not expect biased theoretical conditions; (ii) the city populations were determined rather precisely. The present results show that: (i) the population size growth of the Bulgarian cities is size dependent, whence Hypothesis 1 is not confirmed for Bulgaria; (ii) the population size growth of Bulgarian cities can be described by a double Pareto log-normal distribution, whence Hypothesis 2 is valid for the Bulgarian city system. It is expected that this fine study brings some information and light on other usually considered to be more pertinent countries of city systems. |
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Keywords: | city size Gibrat's law Yule stochastic seed process double Pareto log-normal distribution Zipf's law Bulgarian cities |
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