The simplest answer is that it is a necessary companion to economic growth.

Italian economist Vilfredo Pareto started this line of thinking in economics, and it continues strongly.

http://en.wikipedia.org/wiki/Vil...

Economic inequality is a major thread of research in macroeconomics and there are shelf-loads of books and great papers about it. This is one area where I think economists basically get it right, and the answer is complicated, so I don't want to offer an oversimplified summary. I'll just say... study the economics theory on the subject if you're really interested.

Note that this is relative income inequality and poverty. In real terms, standard of living etc., poverty has been steadily going down if you measure it using concrete things like health, infant mortality, nutrition, risk of famine etc.

Unfortunately the psychological human experience of poverty is more strongly driven by relative perception of poverty than absolute. This explains why families in slums will often go hungry so they can afford cable.

The effect is called "relative deprivation" and the best way to understand is probably in terms of the middle layers of Maslow's pyramid, where the needs are social and therefore vulnerable to relative self-assessments of status, wealth etc.

http://en.wikipedia.org/wiki/Rel...