Measuring Public Policy: Impacts of the Supplemental Security Income Program

Abstract

Enactment of legislation providing a national income floor for aged, blind, and disabled Americans has been cited as a major innovation in welfare policy. But did this innovation have significant consequences? To what extent did executive and legislative decision making represented by the legislation affect welfare outputs beyond normal increments? This study is an effort to measure impacts of the Title XX amendments to the Social Security Act in an interrupted time-series design. Applications of an AutoRegressive Integrated Moving Averages (ARIMA) model (Box and Jenkins, 1970) to indicators of welfare policy outputs aid in solving a number of perplexing problems of time-series analysis and facilitate estimation of effects of the Supplemental Security Income Program. Results of the analysis show that this welfare policy innovation resulted in dramatic, nonincremental changes in consequential aspects of American welfare policy. The importance of this finding for incrementalist theory is a topic of consideration as well as its implications for future policy evaluation.