We show modern information technology (in short IT) is the cause of rising income and wealth inequality since the 1970's and has contributed to slow growth of wages and decline in the natural rate. Hence, the source of most improvements in our living standards also causes social losses and rising inequality.
We first study all US firms whose securities trade on public exchanges. Surplus wealth of a firm is the difference between wealth created (equity and debt) and its capital. We show (i) aggregate surplus wealth rose from -$0.59 Trillion in 1974 to $24 Trillion which is 79% of total market value in 2015 and reflects rising monopoly power. The added wealth was created mostly in sectors transformed by IT. Declining or slow growing firms with broadly distributed ownership have been replaced by IT based firms with highly concentrated ownership. Rising fraction of capital has been financed by debt, reaching 78% in 2015. We explain why IT innovations enable and accelerate the erection of barriers to entry and once erected, IT facilitates maintenance of restraints on competition. These innovations also explain rising size of firms.
We next develop a model where firms have monopoly power. Monopoly surplus is unobservable and we deduce it with three methods, based on surplus wealth, share of labor or share of profits. Share of monopoly surplus rose from zero in early 1980's to 23% in 2015. This last result is, remarkably, deduced by all three methods. Share of monopoly surplus was also positive during the first, hardware, phase of the IT revolution. It was zero in 1950-1962, reaching 7.3% in 1965 before falling back to zero in 1970. Standard TFP computation is shown to be biased when firms have monopoly power.