There's a book called The Media Monopoly that details how all of the media companies in the world have consolidated to just a handful of mega corps and the book had to be republished 5 times since the 80s because every few years the number keeps shrinking dramatically. The author later released a brand new book called The New Media Monopoly which is essentially the 7th edition of the original book and at this point we're in a fucked up late stage version of the problem he originally detailed.