1. Note that the longest lags show a significant difference from the shortest lags, however the estimates of returns to research are larger. It is not clear whether this difference is the result of the different model or a less well conditioned information matrix.
2. These data were collected from several sources, including the Current Research Information System (CRIS) and various annual reports of the Maine Agricultural Experiment Station. Research expenditures, spillover, and extension expenditures are deflated by the Implicit Price Deflator for Gross National Product: Government Purchases of Goods and Services (1977=100) (USDA) to obtain real research expenditures. To allow for the lagged effects and conserve degrees of freedom, MAES expenditures were collected beginning with 1941.
3. The Productivity and Allocation of Research: U. S. Agricultural Experiment Stations, Revisited
4. Norton George W. , Coffey Joseph D. , and Frye E. Berrier “Estimating Returns to Agricultural Research, Extension, and Teaching at the State Level.” Southern Journal of Agricultural Economics (1984):121–28.