Economic question.. Market structures( competitive + concentrated)?

Question

How can I describe the process by which markets tend to drift away from competitive market structures to concentrated structures?

The book is so confusing, and couldn't find any useful information on the web.

Answer 1

Because true competitive markets encourage survival of the fittest, without intervention, the fittest will continue to excell while the others go away.  This will result in concentration of power.  No better example than the phone companies.  AT&T held a monopoly and the government busted it up.  There were new companies all over the country.  Now 20 or so years later the wired phone market is once again concentrated with one of At&T buying two baby bells and then one of the old ones buying all of them.