Having personally dealt with many of these migrants, in a certain capacity, I have things to say.
Not all are economic migrants.
Many I saw were from well off families, were teens who watched some movies and get some ideas about the west, and wanted to go to the west for having the lifestyle they saw in certain movies.
Likewise not all are Pakistani. Many I saw were Indian Punjabi or Afghan pushtoon, using Pakistani documents.
I could tell from many indicators. Such as their knowledge about Pakistan, accent and the language used.
But to a foreigner, they were what documents they had, and Pakistani documents, real or fake , are way too easy to get