The accounts are derived from a wide variety of statistical source data including surveys, administrative and census data, and regulatory data, which are integrated and harmonized in the conceptual framework. They are usually compiled by national statistical offices and/or central banks in each country, though this is not always the case, and may be released on both an annual and (less detailed) quarterly frequency. Practical issues include inaccuracies from differences between economic and accounting methodologies, lack of controlled experiments on quality of data from diverse sources, and measurement of intangibles and services of the banking and financial sectors.   • H. O. Stekler, 1964. "Journal of the American Statistical Association", 59(307), pp. [https://www.jstor.org/pss/2283115 965-967.   • J. Steven Landefeld, Eugene P. Seskin, and Barbara M. Fraumeni. 2008. "Taking the Pulse of the Economy: Measuring GDP." "Journal of Economic Perspectives", 22(2), pp. 193–216. PDF link (press +).   From "The New Palgrave Dictionary of Economics", 2nd Edition, with Abstract links:  • "intangible capital" by Daniel E. Sichel   • "national income" by Thomas K. Rymes.</ref>