The data warehouse is able to collect and coalesce data from various sources. Employee data is generally housed in separate human resource systems based on vertical human resource functions, such as benefits, payroll and compensation, leave, training, performance appraisals and surveys and/or horizontally across functional areas. Companies need to identify all internal and external data sources and then consolidate the data into a human resource data warehouse or, one or more data marts. Some examples of external data sources are US Bureau of Statistics, Open Government Directive Datasets (data.gov), collective agreements, labor market trends, labor regulations, and industry benchmarks.