In economics, business and many other areas sources are very important. Many sources have agendas in publishing certain information, so only use sources that are validated. For example, for GDP, I would use the trusted International Economic data and Statistics such as International Financial Statistics, World Bank Data, and Bloomberg. Take a look at Yale's law library list of 75 sources per the following link of economic data, statistics, reports, and commentary. I hope that this helps!
https://library.law.yale.edu/news/75-sources-economic-data-statistics-reports-and-commentary