Program FACTOR at 10: Origins, development and future directions.

BACKGROUND We aim to provide a conceptual view of the origins, development and future directions of FACTOR, a popular free program for fitting the factor analysis (FA) model. METHOD The study is organized into three parts. In the first part we discuss FACTOR in its initial period (2006-2012) as a traditional FA program with many new and cutting-edge features. The second part discusses the present period (2013-2016) in which FACTOR has developed into a comprehensive program embedded in the framework of structural equation modelling and item response theory. The third part discusses expected future developments. RESULTS at present FACTOR has attained a degree of technical development comparable to commercial software, and offers options not available elsewhere. DISCUSSION We discuss several shortcomings as well as points that require changes or improvements. We also discuss the functioning of FACTOR within its community of users.