The reaction in the $12.8 trillion U.S. government bond market to surprisingly strong data has become more muted in recent months, according to Goldman Sachs Group Inc. At the same time, the influence of unexpectedly weak data has grown for longer maturities, while staying about the same for others, the New York-based bank wrote in a report published Tuesday. “Investors’ pessimism on growth could be playing a role in explaining the decline — and low levels — of U.S. rates,” wrote Silvia Ardagna, who’s based in London.