という研究結果をサンフランシスコ連銀のEconomic Letterが紹介している（H/T Mostly Economics；その結果をまとめた論文はこちら）。 以下はその冒頭部からの引用。 We find that unanticipated increases in highway spending have positive but temporary effects on GSP, both in the short and medium run. The short-run effect is consistent with a traditional Keynesian channel in which output increases because of a rise in aggregate demand, combined with slow-to-adjust pri