  Polynomial distribution can be applied to dynamical systems in certain
situations. Macroeconomic systems characterized by economic variables such as
income and wealth can be modelled similarly using polynomials. We extend our
previous work to data regarding income from a more diversified pool of
countries, which contains developed countries with high income, developed
countries with middle income, developing and underdeveloped countries. Also,
for the first time we look at the applicability of polynomial distribution to
expenditure (consumption). Using cumulative distribution function, we found
that polynomials are applicable with a high degree of success to the
distribution of income to all countries considered without significant
differences. Moreover, expenditure data can be fitted very well by this
polynomial distribution. We considered a distribution to be robust if the
values for coefficient of determination are higher than 90%. Using this
criterion, we decided the degree for the polynomials used in our analysis by
trying to minimize the number of coefficients, respectively first or second
degree. Lastly, we look at possible correlation between the values from
coefficient of determination and Gini coefficient for disposable income.
