Migration, ethnic minorities and network externalities

Thomas de Graaff
(2002) Thela thesis


Four years ago, when I explained to my family that I hoped to become a doctor, most people became rather confused and were convinced that I had entered a medical profession. For years, I was asked to look at swollen ankles and bruised knees. Finally, the notion that I was just continuing my studies gradually became apparent to most of them. Not only to family, but to most people the real meaning of writing a Ph.D. thesis is not easy to grasp. However, family and friends have always stimulated and encouraged me to do whatever I did. Hopefully, this book is the proof that I was not making up all of those stories I told them in the pub, at birthday parties and candlelit dinners. Obviously, this undertaking could not have been done on my own and I would like to take the opportunity here to thank the following people.

In the first place, I would like to thank my supervisor Peter Nijkamp, who, with his boundless enthusiasm, energy and positive attitude, convinced me every time that it was not a mirage that one day I would defend my thesis. Peter also persuaded me to take the Ph.D. position in the first place, a decision I will most probably never regret. Secondly, I owe a great deal of gratitude to my co-promotor, Cees Gorter. He helped me enormously in the first three years of my research, not only in building the research framework but also by spending whole afternoons brainstorming. Cees will always occupy a special place in my heart. I will remember his dedication to economics forever, his humor, and his ability to put things into perspective. In my fourth year, Henri de Groot took over most of Cees’s tasks and I am very grateful for the tremendous effort he put into my dissertation and in guiding me through the last stages. Henri proved to be the ideal sparring partner, not only in economic issues but also in a broader sense.

I have worked closely with Raymond Florax during the last four years and his intuition, honesty and search for perfection has been an example (and mirror) for my own work. Moreover, working with him taught me the precise meaning of the phrase `in the nick of time’, because Chapter 7 was finalized on the evening of my last contract day. Other colleagues whom I would like to mention explicitly are Frank Bruinsma, with his down-to-earth approach, and Aura Reggiani, who taught me the Italian way of living and working.

The first two years of my research were undertaken at the Tinbergen Institute on the Keizersgracht in Amsterdam. A location not without a certain charm. I will remember most the discussions with my roommates Daniel and Egbert, the lack of consistency in working hours and the enormous amounts of coffee we drank. A habit I took with me to the VU. Noteworthy were also the social events and drinks, that had no curfew at that time. Here, I would like to thank Xander, Udo, Paul, Hans, Aico, Matthijs, Arjen, Rutger and Bas for some very enjoyable hours.

In contrast to popular belief, social drinks started to become more frequent at the VU. They took place, of course, in the Bruin Cafe on Friday’s and were, together with the (then) weekly squash events, the occasions to get to know your colleagues better. Days at the VU would have been less amusing without them, so, Ron, Jasper, Barry, Caroline, Joelle, Martijn, Arno, Shunli, Elfie, Trudy, Arianne, Katrin, Galit, Eric and Erik, and numerous other colleagues, thanks for making the last two years even more enjoyable.

The stimulation and encouragement of my friends did not always coincide with my research, but were, nonetheless, probably more important for me than they can ever imagine. They were always willing to brutally attack my latest findings or hypotheses with the subtlety of a sperm whale. For the long evenings and nights, I would especially like to mention Stevin, Manuel, Claartje, Koets, Tessa, Marjolein, Willemijn, Pieter and Rene. Moreover, I would particularly like to thank Jan here, because he was always the one who listened to me when a presentation failed miserably again, when algorithms displayed the nasty habit of not converging, or just when I felt like talking in general.

Naturally, my parents are the ones directly responsible for this thesis. I do not only owe them my existence, but a whole lot more, including a very good life. My sister, Charlotte, contributed a lot to the latter, and I do regret that she can not witness my defense as my paranymph, due to the fact that she is abroad.

Finally, my last words of thanks are for Joyce, my love, who continued believing and supporting me, even though she knew she was not going to be my paranymph. Joyce showed me those other important and wonderful things in life that Ph.D. students sometimes tend to forget.