ANALYZING POLICY IMPACT: SELECTION OF A LINEAR TREND MODEL

Policy analysts, as well as politicians, have shown great interest in assessing both short-term and long-term consequences of public policies in recent years. Recent time-trend studies have attempted to depict the time dimension of policy consequences through extensions of regression techniques. This study examines three linear trend models which have been used to depict policy impact through time-series analyses, and identifies the relative advantages and disadvantages associated with the use of each model. The three models are applied in a quasi-experimental time-series design to time-series of per capita state expenditures for large cities, in eight states, over a twenty-year period. Differences in degrees of multicollinearity and autocorrelation inherent in the three models are discussed, and the model providing the most conservative coefficient estimates is identified.     

Microwear analysis of experimental flint tools: a test case

Recent attempts to infer the functions of prehistoric stone tools have centred on the study of microscopic traces of wear on the surfaces of these tools. One method of “microwear analysis” involving high magnification and an incident light microscope is tested in this paper. Modern flint tools made and used in ways thought relevant to prehistory were produced by a lithic technologist and after cleaning given to the microwear specialist who attempted to infer their use. A high degree of agreement between inferred and actual uses was achieved and this encouraging result has important implications for the study of microwear on prehistoric tools where no such independent check is available.