Riesz regression has garnered attention as a tool in debiased machine learning for causal and structural parameter estimation (Chernozhukov et al., 2021). This study shows that Riesz regression is closely related to direct density-ratio estimation (DRE) in important cases, including average treat- ment effect (ATE) estimation. Specifically, the idea and objective in Riesz regression coincide with the one in least-squares importance fitting (LSIF, Kanamori et al., 2009) in direct density-ratio estimation. While Riesz regression is general in the sense that it can be applied to Riesz representer estimation in a wide class of problems, the equivalence with DRE allows us to directly import exist- ing results in specific cases, including convergence-rate analyses, the selection of loss functions via Bregman-divergence minimization, and regularization techniques for flexible models, such as neural networks. Conversely, insights about the Riesz representer in debiased machine learning broaden the applications of direct density-ratio estimation methods. This paper consolidates our prior results in Kato (2025a) and Kato (2025b).

This note introduces a unified theory for causal inference that integrates Riesz regression, covariate balancing, density-ratio estimation (DRE), targeted maximum likelihood estimation (TMLE), and the matching estimator in average treatment effect (ATE) estimation. In ATE estimation, the balancing weights and the regression functions of the outcome play important roles, where the balancing weights are referred to as the Riesz representer, bias-correction term, and clever covariates, depending on the context. Riesz regression, covariate balancing, DRE, and the matching estimator are methods for estimating the balancing weights, where Riesz regression is essentially equivalent to DRE in the ATE context, the matching estimator is a special case of DRE, and DRE is in a dual relationship with covariate balancing. TMLE is a method for constructing regression function estimators such that the leading bias term becomes zero. Nearest Neighbor Matching is equivalent to Least Squares Density Ratio Estimation and Riesz Regression.

Automatic transistor sizing in circuit design continues to be a formidable challenge. Despite that Bayesian optimization (BO) has achieved significant success, it is circuit-specific, limiting the accumulation and transfer of design knowledge for broader applications. This paper proposes (1) efficient automatic kernel construction, (2) the first transfer learning across different circuits and technology nodes for BO, and (3) a selective transfer learning scheme to ensure only useful knowledge is utilized. These three novel components are integrated into BO with Multi-objective Acquisition Ensemble (MACE) to form Knowledge Alignment and Transfer Optimization (KATO) to deliver state-of-the-art performance: up to 2x simulation reduction and 1.2x design improvement over the baselines.

The health ministry, which is at the heart of the nation's ongoing battle with the coronavirus outbreak, is struggling to keep non-Japanese updated on the rapidly escalating situation in a timely manner, hampered by a dearth of staff proficient in foreign languages. As of Tuesday afternoon, the English version of the ministry's website made no mention of the COVID-19 infection anywhere prominent on its top page, relegating any coronavirus-related links to midpage or lower, with those all directing viewers to original press releases written exclusively in Japanese. "Since our main job has been to update our Japanese website, it has inevitably led to difficulties in providing English-language information in a timely way, so one option is to use machine translation for now," ministry official Takuma Kato said. The official said a future redesign of the English website to better highlight updates pertaining to the new virus is not guaranteed, citing the need to overcome technical difficulties. "Our ministry doesn't have a dedicated team of staff specializing in English-language communication in the first place, so the situation at the moment is that our Japanese staff has been utilizing what little resources they can find to deal with any English update," Kato said.

When a fifth of the people living in the city of Wakayama faced a three-day water stoppage last month to fix a 60-year-old pipe network, they rushed to get ready, only to learn that the repairs could be made without a shutdown. Some 3,000 complaints were filed with city officials, who said they had no way of knowing until they dug up the pipes. Cities across the world are facing similar challenges in dealing with deteriorating infrastructure because of a lack of precision in where and when to fix aging water pipelines. Now, some cash-strapped cities are embracing new technology to make water repairs more efficient, with the goal of cutting construction costs and lowering utility bills. The need is pressing, as global climate change, with an increasing frequency of floods, droughts and warmer weather, is overloading water systems.

At exactly 5 p.m. one recent Friday at Taisei Co., a flying drone alerted workers at the building maintenance firm that the day's work was done. The fully automatic drone, which goes by the name T-Frend, is an example of the unique ways unmanned aerial vehicles are being used to seize control of what people are failing at or incapable of. "This drone will identify who remains in the office after hours. . . . And by accessing recorded data, human resources or administration departments will be able to deal with those who abuse overtime," said Chikara Kato, manager of the Tokyo firm's corporate planning division and inventor of the device. In recent years, Japan has been strengthening efforts to limit overtime amid outrage sparked by the continuing deaths caused by Japan's excessively long working hours.

The government on Friday approved an outline for raising the optional age for tapping public pensions to 71 or older to address the national labor shortage stemming from Japan's falling birthrate and rapidly graying population. The ministry will consider revising the related laws in fiscal 2020 to encourage people in their 60s or older to continue working. The ministry's outline notes that older adults are physically healthier than previous generations and are highly motivated to continue working or participate in community activities. In addition, the outline says the government will review the "standardization of life stages according to age categories." "Depopulation in rural areas is expected as the pace of aging picks up. It is important to realize a society where people of all generations can widely and actively participate," Prime Minister Shinzo Abe said during a meeting on the issue Friday.

The health ministry on Friday approved an outline for raising the optional age for tapping public pensions to 71 or older to address the national labor shortage stemming from Japan's falling birthrate and rapidly graying population. The ministry will consider revising the related laws in fiscal 2020 to encourage people in their 60s or older to continue working. The ministry's outline notes that older adults are physically healthier than previous generations and are highly motivated to continue working or participate in community activities. In addition, the outline says the government will review the "standardization of life stages according to age categories." "Depopulation in rural areas is expected as the pace of aging picks up. It is important to realize a society where people of all generations can widely and actively participate," Prime Minister Shinzo Abe said during a meeting on the issue Friday.

While people fret about robots taking human jobs, machines in Japan are stepping in to fill vacancies amid the worst labor shortage in more than 40 years. That is creating an opportunity for up-and-coming startups focused on automating warehouse tasks. Nitori Holdings Co., the nation's biggest furniture maker, last week deployed 79 robots to move around shelves filled with products at its Osaka distribution center. The company, which introduced the country's first automated furniture warehouse in 1980, is looking to reduce its reliance on human labor. Japan's shrinking pool of workers helped push the number of jobs for every applicant to a ratio of 1.55 in October, the highest since 1973, according to the labor ministry. Inc. have been investing in warehouse automation for years, many Japanese logistics providers are now scrambling to catch up.

Foreign residents in Japan may be at a disadvantage in some ways, but they are by no means powerless nor on their own, says Tokyo-based nonprofit organization Asian People's Friendship Society (APFS). In a recently launched program series, the organization is nurturing a new group of volunteers it calls "foreign community leaders" who will assist fellow non-Japanese trying to navigate life amid a different and foreign culture. "Long-term foreign residents have incredible know-how on how to get by in their everyday lives in Japan," says Jotaro Kato, the head of APFS. "I want people to know that there are foreigners out there who can speak perfect Japanese" and who can provide guidance if needed. Targeting long-term foreign residents with a high level of proficiency in the Japanese language, the 30-year-old organization is spearheading the project to groom such veterans so they can help newcomers overcome a variety of everyday obstacles, such as dealing with language barriers, cultural differences and visa conundrums. For its part, APFS has organized a series of lectures and workshops that are currently taking place every other Saturday in a community hall in Itabashi Ward, Tokyo, in which experts from many different fields discuss topics important to foreign residents.