This might give some insight as to where the 40% comes from (the image shows numbers up to 40%, interestingly) but it's an aggregate number, not violent crimes

This might give some insight as to where the 40% comes from (the image shows numbers up to 40%, interestingly) but it's an aggregate number, not violent crimes per se (it's in Dutch but the infographic is about the numbers anyway): https://www.nrc.nl/nieuws/2016/03/24/een-kaart-om-misdaad-te-snappen-1601239-a890367 https://www.nrc.nl/nieuws/2016/03/24/een-kaart-om-misdaad-te... (I'm assuming that you were referring to the percentage given when you asked for data to back "that" up :)