要旨：本報告では、国立社会保障・人口問題研究所（社人研）で実施した「日本の将来推計人口（令和5年推計）」の推計手法と結果について報告する。前半では、公的推計の役割と方法論（人口投影という考え方、社会経済変数との関わり）、推計時点以降の年齢別人口の推計に必要な年齢別生残率の仮定（死亡仮定）、国際人口移動数（率）の仮定、そして、0歳人口の推計に必要な女性の年齢別出生率の仮定（出生仮定）の設定方法について説明する。後半では、2020年を基準人口とし、2070年まで推計された人口および年齢構成、人口動態数、日本人、外国人別の構成、機械的に仮定条件を変えた条件付き推計の結果を示す。前回推計よりも出生率仮定は低下するものの、平均寿命が延伸し、外国人の入国超過が増加することで、人口減少の進行はわずかに緩和される見込みとなった。出生中位（死亡中位）推計にもとづけば、2070年の日本は、総人口は現在の７割に減少し、65歳以上人口はおよそ４割を占め、外国人人口割合が1割を超える社会となる。

【論文】（10/09更新）

要旨：This paper investigates the elusive role of productivity heterogeneity in new trade models in the trade and environment nexus. We contrast the Eaton-Kortum and the Melitz models with firm heterogeneity to the Armington and Krugman models without heterogeneity. We show that if firms have a constant emission share in terms of sales — as they do in a wide range of trade and environment models — the three models’ emission predictions exactly coincide. Conversely, if firms have a constant emission intensity per quantity — a prominent alternative in the literature — the emission equivalence between the three models breaks. We provide a generalization that nests both constant emission shares in sales and constant quantity emission intensities as special cases. We calibrate the models to global production and trade data and use German firm-level data to estimate the key elasticity of how emission intensity changes with productivity. Our multi-industry quantification demonstrates that the role of firm heterogeneity depends both on the model and the estimated parameters. Moving from the Armington model to the EK model increases the emissions effect on trade, while moving from the Krugman model to the Melitz model decreases the emission effects on trade.

要旨：This study examines the impacts of eliminating school zones, focusing on the commuting behavior of high school students. To address this issue, we exploit the reform of the education system of public high schools in Nagasaki City, Japan. Before the reform in 2002, the local government assigned students to equalize the educational level among schools. While the reform enabled the students to choose a school on their own, the gap in academic performance among schools has widened. We found that one possible reason for this gap is the concentration of students from highly educated areas to schools with location advantages regarding transport accessibility and urban amenities.

【Paper】

Abstract: We explore the impact of public school assignment reforms by building a households’ school choice model with two key features—(1) endogenous residential location choice and (2) opt-out to outside schooling options. Households decide where to live taking into account that locations determine access-to-school—admissions probabilities and commuting distances to schools. Households are heterogeneous both in observed and unobserved characteristics. We estimate the model using administrative data from New York City’s middle school choice system. Variation from a boundary discontinuity design separately identifies preferences for access-to-school from other location amenities. Residential sorting based on access-to-school preference explains 30% of the gap in test scores of schools attended by minority students versus their peers. If households’ residential locations were fixed, a reform that introduces purely lottery-based admissions to schools in lower- and mid-Manhattan would reduce the cross-racial gap by 7%. However, households’ endogenous location choices dampen the effect by half.

要旨：Japan’s economy faces the challenges of demographic aging, with the aging of CEOs being a significant channel. When a CEO cannot find a successor, the firm may be forced to voluntarily exit the market. This study examines the propagation effects of demographic aging by analyzing the correlation between the voluntary exits of firms and their business partners. We hypothesize that the voluntary exit of a firm could lead to the voluntary exit of its business partners, creating a cascading effect throughout the firm network. Using firm-level data and controlling firm characteristics, industry, and year fixed effects, we find a positive and significant correlation between the voluntary exits of owned firms and their business partners. Furthermore, we observe that these effects are more pronounced for firms located in peripheral prefectures, possibly due to lower firm density and diversity, making it harder for firms to find new business partners after the exit of an existing one. This difference between core and peripheral prefectures is particularly strong for linkages between manufacturing firms , which can be attributed to input specificity. Our findings contribute to understanding the impact of demographic aging on firm networks and have implications for industrial policies aimed at maintaining the viability of firms, especially in peripheral areas.

【Paper】5/1改訂版　【資料】5/16掲載　【Slide】5/17掲載

Abstract: Knowledge creation either in isolation or joint with another person, using either face to face or internet contact and incorporating internet search ability is analyzed. Both a conceptual phase and a technical phase of research are analyzed, allowing workers to choose endogenously their mode of communication. In addition to formal knowledge, tacit knowledge plays an essential role in the knowledge production process, as it is not internalized. Lead time for face to face communication plays a key role. The sink point is inefficient. Our framework is applied to pandemic restrictions on face to face communication.

【Paper】【Slides】(5/5更新)

Abstract: Urban informality, which is prevalent in Africa’s rapidly growing cities, can reduce private investments, lower tax bases, and exacerbate urban disamenities. A key policy tool to address this problem is greenfield urban planning where governments purchase cheap agricultural land on the urban fringe and partition it into planned, surveyed, and titled de novo plots, which people can purchase and build houses on. Yet, there is very little systematic evidence on the effects of de novo planning choices, such as the size and configuration of residential and non-residential plots. We study the consequences of such planning decisions in Tanzania’s “20,000 plot” project, which provided over 36,000 residential plots in 12 project areas on the fringes of Dar es Salaam in the early 2000s. We study this project using detailed maps, questionnaires, and satellite imagery, and we combine within-neighborhood analysis and spatial regression discontinuity designs. We find that overall, the project secured property rights and access, thus boosting land values, and attracting highly educated owners; small plots, which command higher land values and are built more intensively, are under-provided; access to main paved roads is prized; and development rates are higher where plot layout is more gridded and small plots are bunched together. But planned non-residential amenities are ignored due to low implementation rates and about half the plots are still unbuilt, suggesting that despite the project’s success, significant improvements are possible.

【スライド】

要旨：本講義では、ネットワーク上の行動のモデリングについて、主に交通分野の経路選択行動分析における経路相関，経路選択肢集合の特定、エージェント間の相互作用（交通混雑）という3つのモデリング上の課題に着目しながら、方法論的発展を概説します。また、それらを同時に解決するマルコフ型ネットワーク均衡モデルや、モデル推定に関する数値計算問題への対処、そして局所的な反応を同時に扱うモデルなど、発表者の近年の取り組みについても紹介し、ネットワーク行動モデルの可能性について議論します。

《参考文献》

Oyama, Hara and Akamatsu, Transportation Research Part B: Methodological, 2022

Oyama, Transportation Research Part C: Emerging Technologies, 2023

Oyama, Transportation Research Part A: Policy and Practice, 2024

【論文】 【スライド】

要旨：Labor force participation of prime-aged males in the U.S. has secularly declined for a half century since 1970s, threatening the formation of partnership and fertility. I test a hypothesis that long-run climate change nudged their labor market exits, a significant fraction of whom are working outdoors under heightened exposure to hot days. Combining granular daily temperature data and labor force participation across U.S. Commuting Zones during 1970-2019, I find that accumulated exposure to hot day with mean temperature 80F accounts for 20-30% of increased non-participation of prime-aged males. Climate change significantly accounts for market exits of black males, historically agglomerated in the Southeast, where warming was severest.