Complex sentence: At the OECD, between 1991 and 1993, he headed the Secretary-General's Task Force on Structural Adjustment, which concentrated on improving the efficiency of government policies in a wide range of areas.
Split into simpler sentences: At the OECD between 1991 and 1993 he headed the Secretary-General's Task Force on Structural Adjustment. This task force concentrated on improving the efficiency of government policies in a wide range of areas.