if only we had a distributed group of people, all of whom with a vested interest in figuring this out, that could help us with doing speed tests in variety of configurations…
A rough look at the data suggests that Verizon DLS used to be around a stable 1.4 Mbps until October 2013 and is on a continuous decline since then with a current low of 1.17 Mbps. That would support the OPs theory, but it's only a single datapoint that may have other underlying causes.
I believe that's a few months after Netflix started heavily using Cogent as a provider, and thus Cogent's peering disputes with Verizon and Comcast began:
My company uses Cogent as an ISP, and remote workers have had nothing but trouble trying to use VPN and other connections back home via Comcast or Verizon because the Cogent/Comcast+Verizon peering points are severely overloaded, dropping packets at a 5%+ clip at some times during the day.
