Asymptotic analysis of the model for distribution of high-tax payers
  The z-transform technique is used to investigate the model for distribution of high-tax payers, which is proposed by two of the authors (K. Y and S. M) and others. Our analysis shows an asymptotic power-law of this model with the exponent -5/2 when a total ``mass'' has a certain critical value. Below the critical value, the system exhibits an ordinary critical behavior, and scaling relations hold. Above the threshold, numerical simulations show that a power-law distribution coexists with a huge ``monopolized'' member. It is argued that these behaviors are observed universally in conserved aggregation processes, by analizing an extended model. 
Hiroshi Yamamoto, Toshiya Ohtsuki, Akihiro Fujihara, Satoshi Tanimoto,   Keizo Yamamoto and Sasuke Miyazima