The average length of a PhD research at Erasmus University is 63 months. They end up in the middle on a ranking of all Dutch universities. The average PhD student in the Netherlands needs 61 months to complete her or his promotion.
That means, PhD students at Erasmus University need about fifteen months longer than the regular four-year contract. It doesn’t always mean they actually need that time extra to finish their research, sometimes there are other reasons. For example, some don’t have a full time contract, so they are allowed to take longer. Some others have a five-year contract. Also, some PhD students have to wait for their defense for a couple of months. All these factors are not taken into account in the figures below.