"You mean wage workers in the formal sector, especially in the North, ...this minority of the global labor force"
Minority, but not such a small one. Old figures, but in 1997 the ILO reckoned that 23 per cent of the industrial workforce was in Europe, a further 6 per cent in the U.S. (= 29 per cent)
Of the total workforce 1995 Europe was 12.9% (354m), US 5.4% (149m) = 18.3 per cent (503m).
Bearing in mind 1. that recent years have seen big employment growth in the US and Europe (both up 20 per cent between 1985 and 2001) and 2. that these numbers do not include the large industrial workforces of S. Korea and Japan, which I think are not shanty dwellers, for the most part.
I don't believe the evidence supports the Third Worldist vision of the Wretched of the Earth, rising up in their shanty towns.
In fact, insofar as the balance of the workforce, and specifically the industrial workforce, has shifted away from the US and Europe, that is being driven by the re-creation of early European style patterns of industrialisation, rather than a growth in the peasantry.
Also, I think you are wrong to dismiss the productivity of the workers in the north, which obviously shouldn't be taken as a moral judgement, it is just the fact that output is greater in the more capitalised economies. That said, over time, the northern economies are losing that advantage as eastern economies become more industrialised.
[Having said that, Doug oversteps the mark- it is Monthly Review's choice who edits their website, not his.]