1. Most important, the sudden fall in gasoline usage rather than it being a steady fall.
2. The concurrent, recent drops in vehicle miles travelled, which is 95% correlated with GDP.
3. That many of the natural gas conversions are being done on vehicles that burn diesel, rather than gasoline, though I'm not sure whether school buses use diesel (city buses do though).
I see school buses use diesel too, so the conversions aren't impacting gasoline usage.
I searched the seattletimes article for the production/consumption data and found it. The numbers I remember from 5 or 6 years ago are 5 and 20, so we now produce nearly a third of our petroleum usage rather than a quarter. Most of the gap is being closed by decreased usage rather than increased production, so it's interesting that most of the article is devoted to how and why production has increased.
The United States produced 5.9 million barrels of crude oil a day in December, while consuming 18.5 million barrels of petroleum products, according to the Energy Department.