This study regresses the log difference over seven days in the number of new confirmed cases of COVID-19 in Japan on lagged values of household expenditures per household on eating out, traveling, admissions to entertainment facilities, clothing and footwear, and the other items, as well as a measure of mobility in public transportation in the past 14 days. The sample period of the dependent variable is set from March 1, 2020, to February 1, 2021, in order to avoid a possible structural break due to the spread of mutant strains in 2021. The regression model is estimated by the Bayesian method with a non-informative (improper) prior. The out-of-sample forecasts of the regression by the posterior means of regression coefficients perform well before the spread of the Delta variant in Japan since June 2021: R2 for the out-of-sample forecasts from February 2, 2021, to June 30, 2021, is 0.60. The estimated model is used to decompose fluctuations in the dependent variable into the contributions from each classified component of household expenditures.

A limited ability of the court to distinguish different qualities of goods of the same kind is introduced into an overlapping generations model. The model shows that fiat money recognizable by the court can circulate as both the means of debt repayments and the means of payments for goods endogenously. The model predicts that private money must be able to substitute the role of the civil court in contract enforcement, in order to replace legal currencies. The recipient of the 2021 JER Best Article Award.

This paper simulates the cash flows and balance sheet of the Bank of Japan (BoJ) before and after the end of Quantitative and Qualitative Monetary Easing (QQE) under various scenarios. The simulations show that the BoJ will record significant accounting losses after the end of QQE, because the yields on Japanese government bonds (JGBs) acquired during QQE will be lower than the interest rate on excess reserves after the end of QQE. These losses are fiscal costs for the consolidated Japanese government, as they correspond to increased interest expenses to the public. The extent of the BoJ's accounting losses depends crucially on the duration of QQE and the interest-rate elasticity of banknote demand. (C) 2017 The Authors. Published by Elsevier B.V.

This paper presents a three-period model featuring a short-term investor in the over-the-counter bond market. A short-term investor stores cash because of a need to pay cash at some future date. If a short-term investor buys bonds, then a deadline for retrieving cash lowers the resale price of bonds for the investor through bilateral bargaining in the bond market. Ex-ante, this hold-up problem explains the use of a repo by a short-term investor, the existence of a haircut, and the vulnerability of a repo market to counterparty risk. This result holds without any uncertainty about bond returns or asymmetric information.

「信用が存在しうる環境でなぜ貨幣が必要になるのか」という研究課題については、「Nominal Contracts and the Payment System」という単著論文を書き上げ、査読付き国際学術雑誌であるInternational Journal of Central Bankingに投稿した。この論文では、貨幣を裁判所が認識できる債務返済手段（法貨）として位置づけ、その結果、貨幣が財市場での支払手段として使用され、また、日中当座貸越など、現在実際に行われている中央銀行による弾力的な貨幣供給が必要になることを理論モデルで導出した。介護のような社会保険支出の相互保険の機能を、法定通貨とは別の貨幣を社会に導入することで代替できるかについては、「Elderly Care and Multiple Monies」という早稲田大学現代政治経済研究所ワーキングペーパーの改訂作業を行った。

当該研究費により、東北大学で開かれた２０１５年日本金融学会秋季大会における非伝統的金融政策のセッションに出席した。その知見を活かし、日本銀行の「量的・質的金融緩和」が日本銀行のバランスシートに与える影響についての長期シミュレーションを行った。分析結果は２０１６年８月のNBER Japan Projectカンファレンスで報告される予定である。また、平行して、中央銀行が商業銀行に日中当座貸越をする必要があるようなlimited participationを標準的なマクロモデルである新古典派成長モデルに簡易な形で導入することに成功した。この結果は２０１６年４月東京大学でのマクロ経済学ワークショップで発表される予定である。