To be able to read emails in the train on the way to work and home, order shopping, Whatsapp with friends and business relations. Many users will undoubtedly say their productivity has risen sharply through the iPhone. In macroeconomic terms, however, this perceived increase in productivity cannot be proven. But: "I can not imagine any other innovation that has been adopted so quickly by the market. The smartphone has become a necessity" says Cor Molenaar.