I recently ran a poll on Twitter to learn how much time it takes it get a PhD – in number of years. The results are sort of expected: 1/3rd takes less than 4 years, 1/3rd between 4 and 5 years, and 1/3rd takes more than 5 years. For the US, there is information here as well. In the Netherlands, PhD trajectories take longer: only 10% finishes within four years.
The wake of this poll and results are here: