What industry consolidation happened over the past 10 years? We still have 4 major carriers then as we do today. The only difference is there are more MVNOs. But they still ride on either a Verizon, AT&T, T-Mobile, or Sprint network.
Over the past 11 years? Ok, easy.
-Verizon buys Alltel. That consolidation benefitted AT&T as well, as they filled in their massive Mid West gaps. This also increased their overall subscriber hold at the time from a combined 50% to 60%. (13 million subscribers)
-Pocket Communications was acquired by Cricket // Leap Wireless
-Cellular One PA was bought by Verizon Wireless
-Corr Wireless was bought by AT&T
-Element was bought by AT&T
-Metro PCS was bought by T-Mobile (10 million subscribers)
-Clearwire was fully bought by Sprint (11 million subscribers)
-Leap Wireless (Cricket) was bought by AT&T (5 million subscribers)
-Cincinatti Bell, all spectrum assets bought by Verizon
-Cellular One IL, bought by AT&T
-iWireless, bought by T-Mobile
Intentionally left off, but perhaps the most important one of them all. AT&T buys T-Mobile. Pulls out of the deal rather than press forward and potentially have to defend it in court, and hands over massive spectrum holdings and 4 billion dollars in cash... both of which allowed them to be as aggressive as they are today.
There are not 4 national carriers. There's 2 with a slowly emerging 3rd -- and that 3rd looks more like AT&T and Verizon 15 years ago than it does them today. There's also many many many other acquisitions during this time that I just didn't feel necessary to list that allowed AT&T and Verizon to be truly national carriers. The merger of T-Mobile and Sprint will create a 3rd. A 3rd mind you, that will still be considerably smaller than the other 2 -- Verizon and AT&T are 3x the size of Sprint and double T-Mobile. They'll still be 30 million customers shy of them after, but in a much safer financial position and able to threaten them even more.
Going back 15 years, we're now in Sprint buying Nextel territory and just 1 year outside Cingular buying AT&T. In that decade, prices fell 50% from what they were in 1999... after the wild consolidation of the 90s which is far too large to even write out here, you'll have to Google yourself to get all the ultra-regional carriers names.