This chapter discusses aspects of data sources for budgeting and forecasting. It provides empirical evidence on the preference for data sources for a sample of experienced managers in the context of sales predictions. The authors show that managers still have strong preferences for traditional accounting data sources relative to non-traditional data sources. These preferences change between levels of education. Furthermore, the credibility (and not their use) of social media positively influences the preference for non-traditional data sources. These findings indicate that non-traditional data sources appear to coexist and become complementary to traditional accounting sources and do not substitute them.