と相まってFactors combining to produce a result
と相まって says that two or more factors interact or reinforce one another to produce a result. The combined effect may be favorable or unfavorable.
The key idea: a joint effect
The factors must do more than simply exist at the same time. They should interact, strengthen one another, or jointly shape the result that follows. The sentence therefore works best when the connection between the factors and the result is substantial and easy to see.
Three common frames
The expression can name both factors together, link one factor back to earlier context, or mark one factor as joining other circumstances.
優れた脚本と俳優たちの繊細な演技が相まって、作品は高い評価を得た。
The excellent script and the actors' sensitive performances worked together to earn the production high praise.
AnalyzeBoth contributing factors are stated explicitly.
この地域では若者の流出が続いている。少子化と相まって、地域経済の縮小が加速している。
Young people continue to leave this region. Combined with the falling birthrate, this is accelerating the contraction of the local economy.
AnalyzeThe other factor—the continued departure of young people—is supplied by the preceding sentence.
原材料費の高騰に加え、人手不足も相まって、多くの飲食店が値上げを余儀なくされた。
Rising raw-material costs, compounded by labor shortages, forced many restaurants to raise their prices.
AnalyzeThe marked factor joins the previously named cost increase and worsens the outcome.
Joint effect versus simple addition
に加えて adds another fact or item. と相まって makes the stronger claim that the factors work together and matter jointly to the result.
高性能な断熱材と効率的な換気システムが相まって、建物の消費電力が大幅に減った。
The high-performance insulation and efficient ventilation system worked together to reduce the building's power consumption substantially.
AnalyzeThe sentence presents the two features as jointly producing the reduction.
高性能な断熱材に加えて、屋上には太陽光パネルも設置されている。
In addition to high-performance insulation, solar panels have also been installed on the roof.
AnalyzeThis merely adds another feature; it does not assert that the two features interact to produce a particular result.
More examples
温暖な気候と交通網の整備が相まって、この地域は年間を通じて多くの観光客を集めている。
The mild climate and improved transport network work together to attract many tourists to the region throughout the year.
Analyze政府の支援策への評価が広がり、景気回復への期待も相まって、株価は上昇を続けた。
Growing approval of the government's support measures, together with expectations of an economic recovery, kept stock prices rising.
Analyze長引く干ばつと設備の老朽化が相まって、水不足は一段と深刻になった。
The prolonged drought and aging infrastructure combined to make the water shortage even more serious.
Analyze新製品は操作性を大幅に改善した。洗練されたデザインと相まって、幅広い層から支持を集めている。
The new product greatly improved ease of use. Combined with its sophisticated design, this has won support from a broad range of consumers.
Analyze異なる分野の知見と豊富な現場データが相まって、実用性の高い分析が可能になった。
Knowledge from different fields and abundant field data worked together to make highly practical analysis possible.
Analyze夜間の視界の悪さと激しい雨が相まって、事故の危険性が高まった。
Poor nighttime visibility and heavy rain combined to increase the risk of accidents.
Analyze