is prone to overestimation and partly mediated by demographic characteristics and improvements in housing that are independent from school boundaries. Research on teacher effectiveness The effectiveness of teachers constitutes a third area of Kane's research. Criticizing the lack of improvement in U.S.-American teachers' effectiveness, Kane, Staiger and Robert J. Gordon suggest to (i) reduce entry barriers to teaching, (ii) increase barriers to tenure, (iii) award bonuses to highly effective teachers willing to teach at disadvantaged schools, (iv) measure teachers' job performance, and (v) track student performance and teacher effectiveness over time. Comparing different methods to estimate teachers' impacts on student achievement, Kane and Staiger argue for the impact to be estimated most accurately if both prior student test scores and mean classroom characteristics are considered; they find that teacher-specific effects fade by about half each year after teachers' initial assignment to a class. Moreover, in further work with Jonah Rockoff, Kane and Staiger find that - unlike teachers' performance in classrooms during the first two years - teacher certification poorly predicts teachers' future effectiveness. Together with Brian Jacob, Kane, Staiger and Rockoff also observe that composite measures of teachers' cognitive and non-cognitive skills predict well teachers' effectiveness, though individual measures do not. Finally, in joint work with John Tyler, Eric Taylor and Amy Wooten, Kane finds classroom-based measures of teaching effectiveness to be good predictors of student achievement (though some teaching practices predict achievement more than others), leading him to suggest that teacher evaluations should use both classroom observations and student test scores. More recently, Kane has published extensively on the measurement of teacher effectiveness as part of his involvement in the Bill and Melinda Gates Foundation's Measuring Effective Teaching (MET) project. In particular, Kane and Staiger found that (i) measures of teaching effectiveness such as FFT, CLASS, PLATO, MQI, and UTOP are positively correlated with student achievement gains; (ii) the reliable assessment of teacher's practices necessitates the averaging of scores over multiple observations, (iii) the combination of observation scores with evidence of student achievement gains and student feedback is more predictive and reliable; (iv) unlike teaching experience and graduate degrees, the combined measure identifies teachers with larger gains on the state tests; and (v) teachers performing strongly on the combined measure also performed well in terms of their students' in-class effort, enjoyment and gains in terms of math comprehension and literacy. Later research by Kane and his MET co-researchers