  We investigate the Japanese personal income distribution in the high income
range over the 112 years 1887-1998, and that in the middle income range over
the 44 years 1955-98. It is observed that the distribution pattern of the
lognormal with power law tail is the universal structure. However the indexes
specifying the distribution differ from year to year. One of the index
characterizing the distribution is the mean value of the lognormal
distribution; the mean income in the middle income range. It is found that this
value correlates linearly with the Gross Domestic Product (GDP). To clarify the
temporal change of the equality or inequality of the distribution, we analyze
Pareto and Gibrat indexes, which characterize the distribution in the high
income range and that in the middle income range respectively. It is found for
some years that there is no correlation between the high income and the middle
income. It is also shown that the mean value of Pareto index equals to 2, and
the change of this index is effected by the change of the asset price. From
these analysis we derive four constraints that must be satisfied by
mathematical models.
