The composite additive approach, which is based on tangible, observed practices, is more appropriate for teacher professionalism than other approaches, such as confirmatory factor analysis or structural equation modelling, which rely on inter-item correlations to capture a latent construct (such as, for example, job satisfaction). Figure 2.1 plots system-level values of the TALIS teacher professionalism index against student performance in the PISA 2012 mathematics assessment. The trend line suggests that there is a weak, positive relationship between the overall values on the teacher professionalism index and an education system's learning outcomes.