In probability theory, the stable count distribution is the conjugate prior of a one-sided stable distribution. This distribution was discovered by Stephen Lihn (Chinese: 藺鴻圖) in his 2017 study of daily distributions of the S&P 500 and the VIX. The stable distribution family is also sometimes referred to as the Lévy alpha-stable distribution, after Paul Lévy, the first mathematician to have studied it.
Of the three parameters defining the distribution, the stability parameter α {\displaystyle \alpha } is most important. Stable count distributions have 0 < α < 1 {\displaystyle 0<\alpha <1} . The known analytical case of α = 1 / 2 {\displaystyle \alpha =1/2} is related to the VIX distribution (See Section 7 of ). All the moments are finite for the distribution.