This is a data set on state-level estimates for the "ruggedness" of a state's terrain.

## Usage

rugged

## Format

A data frame with 192 observations on the following 6 variables.

ccode

a Correlates of War state code

gwcode

a Gleditsch-Ward state code

rugged

the terrain ruggedness index

newlmtnest

the (natural log) percentage estimate of the state's terrain that is mountainous

## Details

The data-raw directory on the project's Github contains more information about how these data were created. It goes without saying that these data move slowly so the data are really only applicable for making state-to-state comparisons and not states-in-time comparisons. The terrain ruggedness index is originally introduced by Riley et al. (1999) but is amended by Nunn and Puga (2012). The mountain terrain data was originally created by Fearon and Laitin (2003) but extended and amended by Gibler and Miller (2014). The data are functionally time-agnostic---use with caution in your state-year analyses---but all data sets seem to benchmark around 1999-2000. I'm not sure it matters that much, but it matters a little at the margins, I suppose, if you suspect there are major differences in interpretation of how much more "rugged" the Soviet Union was than Russia, or Yugoslavia than Serbia.

## References

Fearon, James D., and David Laitin, "Ethnicity, Insurgency, and Civil War" American Political Science Review 97: 75–90.

Gibler, Douglas M. and Steven V. Miller. 2014. "External Territorial Threat, State Capacity, and Civil War." Journal of Peace Research 51(5): 634-646.

Nunn, Nathan and Diego Puga. 2012. "Ruggedness: The Blessing of Bad Geography in Africa." Review of Economics and Statistics. 94(1): 20-36.

Riley, Shawn J., Stephen D. DeGloria, and Robert Elliot. 1999. "A Terrain Ruggedness Index That Quantifies Topographic Heterogeneity,” Intermountain Journal of Sciences 5: 23–27.