Champernowne distribution
In statistics, the Champernowne distribution is a symmetric, continuous probability distribution, describing random variables that take both positive and negative values. It is a generalization of the logistic distribution that was introduced by D. G. Champernowne.[1][2][3] Champernowne developed the distribution to describe the logarithm of income.[2]
Definition
The Champernowne distribution has a probability density function given by
where are positive parameters, and n is the normalizing constant, which depends on the parameters. The density may be rewritten as
using the fact that
Properties
The density f(y) defines a symmetric distribution with median y0, which has tails somewhat heavier than a normal distribution.
Special cases
In the special case it is the Burr Type XII density.
When ,
which is the density of the standard logistic distribution.
Distribution of income
If the distribution of Y, the logarithm of income, has a Champernowne distribution, then the density function of the income X = exp(Y) is[1]
where x0 = exp(y0) is the median income. If λ = 1, this distribution is often called the Fisk distribution,[4] which has density
See also
References
- ↑ 1.0 1.1 C. Kleiber and S. Kotz (2003). Statistical Size Distributions in Economics and Actuarial Sciences. New York: Wiley. Section 7.3 "Champernowne Distribution."
- ↑ 2.0 2.1 Champernowne, D. G. (1952). "The graduation of income distributions". Econometrica 20: 591–614. JSTOR 1907644.
- ↑ Champernowne, D. G. (1953). "A Model of Income Distribution". The Economic Journal 63 (250): 318–351. JSTOR 2227127.
- ↑ Fisk, P. R. (1961). "The graduation of income distributions". Econometrica, 29, 171–185.