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Fractional Integration Methods in Political Science Box-Steffensmeier, Janet M. Uploaded 05-02-1999 Keywords Fractional integration fractional cointegration congressional approval Abstract Controversies in researching political time series often revolve around the best characterization of the series, i.e., whether a series is stationary or integrated. By using a fractional integration approach, one can avoid this controversy. Fractionally integrated series are mean-reverting, but decay at different rates than a stationary series. Theoretical reasons may also lead one to expect a fractionally integrated series. Estimation of the d parameter in an ARFIMA (p, d, q) model is no longer difficult and multivariate extensions are proving useful. Using fractionally integrated methods can lead to substantive and methodological insights about political processes. We estimate d for congressional approval and economic expectations data from Durr, Gilmour, and Wolbrecht (1997) and test for fractional cointegration.