Why there are rich and poor?

This question has been haunting my mind for quite a while a now.  After all why there is so much of difference between rich and poor?  The world’s wealth is concentrated only in the hands of a small portion of the population.  On the one hand there are people who got no clue how to spend his enormous wealth and on the other hand some people find it really hard to have food at least twice a day.  While some people enjoy life in luxurious huge bungalows, others sleep in footpath in chilling cold even without a blanket.

After all it is said that we all are children of God, then why there are  two categories – the rich and the poor.  The fact is that all socio-economic conditions are favorable for the rich to become richer and poor becomes poorer.  It is indeed a vicious circle of poverty I believe.