New Delhi, April 28 -- Prices in the $31 trillion U.S. Treasury market have been steady for so long that traders fear a sharp change in rates is coming-rather than a slow drift-once a major catalyst hits.

The Treasury market has been quiet lately, with 10-year debt barely straying from a yield of 4.3% in April. For traders, that means chances to make money from changes in U.S. debt prices have been nearly nonexistent. Yields move in the opposite direction of prices.

Bollinger Bands provide additional evidence of market calm. The technical indicator measures volatility by taking an average of yields over the past 20 days. Then it envelopes it with two bands-one above and another below the average. The theory is that when the bands compre...