Barend Abeln began his career at Unilever (Rotterdam, Netherlands) in the economics department, where he reported on macroeconomic developments in European countries. Subsequently, he became a product manager at Unilever Frozen Foods (Utrecht). In 1972, he entered the real estate market as a founder and CEO of Vlakland Planontwikkeling BV, realizing five second-home projects and a hotel on the French Côte d'Azur. In 1982, he became a private investment consultant in Amsterdam and developed a state-of-the-art seasonal adjustment process.

Jan P.A.M. Jacobs studied econometrics at the University of Groningen (Netherlands) and played volleyball at international level (46 international matches). After a brief position at Philips Medical Systems, he returned to his alma mater and received his Ph.D. on "Econometric Business Cycle Research" in 1998. He is an associate professor at the Faculty of Economics of the University of Groningen, where he taught applied macroecometrics to research master students and supervises bachelor, master graduate theses.

He published more than forty articles in peer-reviewed journals in economics (Journal of Econometrics, Journal of Applied Econometrics, Journal of Business & Economic Statistics, Macroeconomics Dynamics, Scandinavian Journal of Economics, Journal of Macroeconomics), law (International Journal of Law in the Built Environment), and medicine (BMC Family Practice, Economics and Human Biology).

Chapter 1. Introduction.- Chapter 2. CAMPLET: Seasonal adjustment without revisions.- Chapter 3. Seasonal adjustment of economic tendency survey data.- Chapter 4. Residual Seasonality: A Comparison of X13 and CAMPLET.- Chapter 5. COVID-19 and Seasonal Adjustment.- Chapter 6. Seasonal adjustment of daily data with CAMPLET.- Chapter 7. Conclusion