AR(1) growth model parameter stability

One of my earlier posts looked at autoregressive parameter stability in the AR(1) growth model for a few countries. This post investigates the stability for all countries in the Penn World Table dataset over 1950-2000. The model used was augmented Solow under an MRW specification, tested at five year intervals, for each country individually using an AR(1) specification rather than the usual panel estimation:

ln income in year t = a + b.ln income in year t-5 + c.ln savings rate average between t-5 and t + d.ln years of education among population aged 15 or older at t + e.ln (population growth in previous five years + 0.05).

The 0.05 is an adjustment for technology growth and depreciation. a,b,c,d,e are constants for estimation. Estimation was by maximum likelihood.

99 countries have sufficient data to allow estimation of the autoregressive parameter, b. The mean was -0.28, and the standard deviation was 0.55. The parameter is not stable across countries, nor does it seem to exhibit any clear distribution. Here is a histogram of the parameters: