Results using a binary indica tor for whether the society is diverse at all

Results using a binary indica tor for whether the

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a society would have two or three levels of jurisdiction. Results using a binary indica- tor for whether the society is diverse at all (equivalent to whether it is intersected by a divide) are similar. Finally, because some of the ecological types recorded in White’s map are similar, potentially leading to over-estimation of ecological diversity, I collapse these classifications into eight “simpler” types. 9 Results are again similar, though the ef- fect of ecological diversity becomes marginally insignificant when regional fixed effects are added. Simplifying the classes in this manner does not do away with the sharply bi-modal distribution of diversity. In addition, the FAO-GAEZ project created its own separate classification of ecologi- cal zones that can be used to construct an alternative diversity measure. 10 This source categorizes raster points in Africa into eleven “dominant ecosystem classes.” 11 For each ethnic group in the data, I construct a measure analogous to that in (1) using the share of raster points for each ecosystem class, rather than the share of area. Results using this alternative measure of ecological diversity are presented in Table 6. As with the distance from an ecological divide, the coefficient estimates here are more statistically robust than main results. 4.3. Validity of the estimation. There are many possible reasons the approach taken to the estimation may be questioned. First, the “parallel regression” assumption of the standard ordered probit model, that the explanatory variables have the same impact on 9 Mountain if altimontane, other if anthropic, water or azonal, bushland if bushland and thicket or bush- land and thicket mosaics, shrub if cape shrubland, transitional scrubland or grassy shrubland, desert if desert or semi-desert, grassland if grassland, secondary wooded grassland or edaphic grassland mosaics, forest if forest or forest transitions and mosaics, and woodland if woodland or woodland mosaics and transitions. 10 This is plate 55, downloaded from . 11 These are Undefined; Grassland; Woodland; Forest; Mosaics including crops; Cropland; Intensive crop- land; Wetlands; Desert, bare land; Water and coastal fringes; Ice, cold desert, tundra; and Urban agglom- erates.
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14 JAMES FENSKE T ABLE 8. Robustness: Influential observations [Table 8 here] the latent index at all points, is often violated in real data. In Table 7, I re-estimate the main results using a generalized ordered probit model (Maddala, 1986), in which the co- efficients on the latent variables are allowed to vary with the points where the categories of the dependent variable are separated. Convergence could not be achieved with re- gional fixed effects, so this specification is not reported. As before, ecological diversity predicts greater state centralization. Here, it is clear that this effect is not confined to any single level of centralization. Excepting at four levels, for which few observations exist, the effect is positive throughout.
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