The selloff in U.S. Treasurys has been going on for months, but it has moved through several different phases.

Just a few weeks ago, yields were rising much faster on short-term Treasurys than long-term Treasurys, reflecting escalating expectations for how high the Federal Reserve will raise short-term interest rates. But that's shifted in recent days: since Sept. 23, the yield on the 10-year note has climbed more than 0.2 percentage point while the 2-year yield has actually dropped around 0.04 percentage point, causing what is known on Wall Street as a steepening yield curve.

One turning point occurred on Sept. 29 when New York Fed President John Williams suggested that an October rate hike was likely unnecessary. Since then, traders have further scaled back bets on an October hike, keeping short-term yields in check, but elevated energy prices and signs of resilient economic growth have continued to put upward pressure on longer-term yields.