After completing his studies, he worked in international sales and marketing at Lorenz von Ehren in Hamburg, Germany.
In 1994, he enrolled at Henley Management College, England, and graduated with a master's degree in Business Administration.
His dissertation was one of the first academic research studies that dealt comprehensively and empirically with the topic 'Customer Lifetime Value'.
After receiving his doctorate in 1999, he started his academic career at INSEAD in Fontainbleau, France, where he worked until 2007.
In 2007, he was appointed a Chaired Professor of Business Administration, Retailing and Customer Management at the University of Cologne and remains till present.