Van der Knoop is interested in the network of interlocking directorates in the Netherlands. He collected data about Dutch directors for the year 1984 from Financieel Economisch Lexicon 1985. He selected 114 industrial and trade companies that belong to the 151 largest Dutch companies (ranked by revenue). Besides he selected the 16 largest banks and 13 largest insurance companies (ranked by assets). He collected the names, functions, title, year of birth of directors of 144 Dutch companies. There are 727 interlocking directorates among the 144 companies. 42 persons (3,5% of all persons included) have four board positions or more, i.e. this small group is responsible for 64% of all interlocks.