Complex sentence: A Norwegian study covering the period 1980 to 2003 found welfare state spending correlated negatively with student achievement, Many of the top-ranking OECD countries on the 2009 PISA tests, however, are considered welfare states.
Split into simpler sentences: A Norwegian study covering the period 1980 to 2003 found welfare state spending correlated negatively with student achievement. However, many of the top-ranking OECD countries on the 2009 PISA tests are considered welfare states.