Software factories seek to develop quality software in a manner comparable to the production of other industrial products, establishing improvements in their production process so as to be more competitive. Productivity, one of the competitiveness pillars, is related to the effort required to fulfill assigned tasks. However, there is no standard way of measuring productivity, making it difficult to establish policies and strategies to improve the factory. In this article, the authors perform a systematic review of the literature on factors affecting productivity of software factories, and models for measuring it. For the period 2005-2017, 74 factors and 10 models are identified. Most of the factors are related to Programming, and a few to Analysis and Design and Testing. Also, most models for measuring productivity only consider activities concerning programming.