I'm with Ste on this one in asking why you wish to know.
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Your question has two presuppositions in it - that there is a high velocity of the drug gangs now (presumably in comparison with somewhere else in your mind?) and that violence seems to have been so prevalent in the last decade in Liverpool (again compared to where? London? Manchester? Brooklyn? Cheadle Hume? Gloucester?)
You appear to be pre-judging quite significantly if you are doing a genuine piece of research.
Perhaps if you give a bit of background and more neutral phrasing????
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