Netflix today made good on a promise from its financial statements yesterday, and it released data on which US Internet providers offer the best access to Netflix streaming content. The company's data puts it "in the unique position of having insight into the performance of hundreds of millions of long duration, high-definition video streams delivered over the Internet."

The chart below sums up the US results; it's a "time-weighted bitrate metric" that shows throughput from Netflix content delivery networks to subscriber homes. Netflix says that its best quality HD streams are encoded at 4,800Kbps, and it's clear from the chart that no ISPs can sustain this level of service across an entire movie. But "the higher the sustained average, the greater the throughput the client can achieve, and the greater the image quality over the duration of the play," says the company.

In the US, Charter delivers the best performance over time (2,667Kbps average), with Comcast, Cox, and Time Warner Cable taking the next three spots.

The disparity between the top and bottom ISPs is stark; Clearwire offers only about half the sustained throughput as Charter (as a wireless operator, this is expected), but wireline ISPs like Frontier and CenturyTel also perform poorly (both companies do have large rural footprints, however).

Despite the constant carping we hear from our Canadian readers about the country's major ISPs, those ISPs do deliver better throughput than the Americans. Rogers leads all ISPs in both countries with a 3,020Kbps average throughput, while Shaw comes just behind.

Netflix has promised to update the charts monthly, which may exert at least a bit of pressure on ISPs who might be tempted to throttle or otherwise downgrade Netflix quality.