In fact, there are two elements to your challenge. There is the historic element (did elimination of the spectrum cap create or substantially contribute to the current distribution of residential customers), and the forward looking policy element (would spectrum caps actually enhance competition and be a worthwhile policy to adopt for upcoming spectrum auctions). Without the second (and unstated) half, the answer is simply an academic exercise.

Unfortunately, an honest effort to address this question would take me a couple of hours. And the answer would still be ambiguous, because demonstrating causality in a complex environment like this is always a challenge. Spectrum caps are one element, as was the phenomenally poor management of the Sprint Nextel merger. I can state with fair confidence that Verizon and AT&T would not have grown to their present size and subscriber base had spectrum caps blocked acquisition of Altell by VZ and Dobson and Centennial by AT&T. But these are glib answers to a question deserving of more complex response. But it is equally as glib, and therefore incomplete, to say that because Sprint Nextel bungled their merger, the elimination of spectrum caps was not a seminal event reshaping the industry over the last 5 years.

Hopefully, I will find the time in the next few days to answer more fully on my blog. Interestingly, it is easier to make the case for imposing new spectrum caps, without regard to the historic impact of the removal of spectrum caps. This is because spectrum caps would no longer be prophylactic. They would prevent expansion by acquisition (as opposed to by customer migration) by either of the two largest firms, and would allow the existing also-rans to match capacity by acquiring new spectrum licenses at auction.