It depends what you mean by manipulated . But ultimately we have to try and work out the best estimate we have with the limited information we have . If you ' re claiming that nonmanipulated data on this doesn ' t exist , you can ' t also be certain that immigration really is the only thing that matters for wages . How could you know that ? If you ' re interested , I wrote a post in rbadeconomics on how econometricians try to isolate the effect of immigration on wages . It ' s a difficult and imperfect process , and there is continued debate about it , but I think it ' s better than everyone just assuming that immigration either has no effect or has a massive effect based on nothing but their prior beliefs and some casual observation filtered through their confirmation bias .