由于衡量美国服务业活动的一项指标不佳，美国国债收益率跌至四个月低点，而空头回补加剧了这一走势。
基准10年期美债收益率周二一度下跌8个基点，落至1.35%下方，创2月24日以来最低水平。30年期美债收益率跌至1.971%，考验200日移动均线。之前公布的6月ISM服务业指数从5月纪录高点回落，降幅超出预期。
“过去一周美债市场对数据的巨大反应以及通胀保值债券(TIPS)市场的寂寥反应表明空头回补放大了走势，” Jay Barry等摩根大通策略师在给客户的一份报告中写道。该行最近开展的美债客户调查显示，空头头寸规模已逼近年内高点。
一些华尔街分析师因为此次涨势改变了看法。道明证券策略师放弃了对做空10年期美债的建议，称“空头回补和夏季清淡交投可能加剧”涨势。
供需因素也利好债市。本周美国财政部拍卖表上的唯一品种是短期国债。投资者也在等待周三美联储会议纪要的发布，以期了解与货币政策前景有关的更多细节。
ISM调查反映出的服务业扩张速度放慢表明美债上涨有一定的经济基础。BMO Capital Markets策略师Ian Lyngen和Benjamin Jeffery在报告中写道，美债收益率的下行也反映了“美国经济目前的增长势头只是暂时性”的观点。
Treasury yields fell to a four-month low due to a poor measure of US service sector activity, a trend exacerbated by short covering.
The yield on the benchmark 10-year u.s. bond fell as much as 8 basis points on Tuesday to below 1.35%, its lowest level since Feb. 24. The yield on 30-year Treasuries fell to 1.971%, testing the 200-day moving average. The previously released ISM services index fell more than expected in June from a record high in May.
"the strong reaction of the US bond market to the data over the past week and the lacklustre reaction of the inflation protected bond (TIPS) market suggest that short covering has magnified the trend," said JPMorgan Chase, such as Jay Barry.The strategist wrote in a report to clients. The bank's recent survey of US debt customers shows that short positions are nearing their highest levels of the year.
Some Wall Street analysts changed their minds because of the rally. Dow Securities strategists abandoned advice on shorting 10-year Treasuries, saying "short covering and light summer trading could exacerbate" the rally.
Supply and demand factors are also good for the bond market. The only item on the Treasury auction table this week is short-term Treasuries. Investors are also waiting for the minutes of Wednesday's Fed meeting to be released for more details about the outlook for monetary policy.
The slowdown in service sector expansion reflected in the ISM survey suggests that there is some economic basis for the rise in US debt. The decline in U.S. bond yields also reflects the view that "the current growth momentum in the U.S. economy is only temporary," BMO Capital Markets strategists Ian Lyngen and Benjamin Jeffery wrote in the report.
