For each measurement, three years have been combined and a (weighted) average has been calculated for these years. The first measurement comprises the years 2003, 2004 and 2005. These years have been selected because of the commencement of the knowledge migrant scheme in 2004. The period 2003-2005 reflects the situation around the start of this scheme. The second measurement comprises the years 2016, 2017 and 2018. These are the most recently available years, providing the most up-to-date picture possible.