Notes on the Theory of Imperialism http://mrzine.monthlyreview.org/2010/bs240610.html

One can no longer today speak of either industrialists or bankers as the leading echelon of the dominant capitalist classes. The big monopolistic corporations, which were formed and in their early years controlled by bankers, proved to be enormously profitable and in due course, through paying off their debts and plowing back their earnings,

achieved financial independence and indeed in many cases acquired substantial control over banks and other financial institutions. These giant corporations are the basic units of monopoly capitalism in its present stage; their (big) owners and functionaries constitute the leading echelon of the ruling class. It is through analyzing these corporate giants and their interests that we can best comprehend the functioning of imperialism today.