Dataset:  oil_nationalize.dat

Source: S.J. Kobrin (1985). "Diffusion as an Explanation of Oil Nationalization:
 Or the Domino Effect Rides Again," The Journal of Conflict Resolution,
Vol 29, #1, pp. 3-32.

Description: Numbers of Countries nationalizing petroleum services
(production, refining, and marketing) annually over years (1960-1979).

Diffusion Model: N(t) = B0 + B1*Y(t-1) + B2*(Y(t-1))^2 for years 1961-1979,
where N(t) = Number of new cases in year t, Y(t-1) is cumulative cases
throuth year t-1. Diffusion Theory: B0, B1 > 0; B2 <0.

B0 = p*m     B1 = q-p    B2 = -q/m
Where:
p = coefficient of innovation
q = coefficient of imitation
m = total # of "purchasers"

m = [-B1 +/- sqrt(B1*22 - 4*B0*B2)] / [2*B2]
q = -m*B2
p = B0/m

Can test Poisson vs Contagious Poisson model also.

Variables/Columns
Year    5-8
Year index  15-16  /* 1960=0  */
# of Nationalizations    23-24
Cumulative previous Nationalizations   30-32