2322 GMT - The U.S. buyback of longer-dated debt, while immediately reducing 30-year bond yields by about 7 basis points, is relatively small, says Kieran Davies, chief macro strategist at Coolabah Capital. While the purchase of bonds and open-ended comments by policymakers can have a sustained effect on yields, the purchases usually have to be extremely large to have significant effect, he says. The Treasury announcement also does nothing about the drivers of higher bond yields, such as the demand for debt from government and tech companies, and the continuing risk of that inflation stays above the 2% target, he adds.