正解: ACorrect: A
格差の大きい社会ほど、生まれた家庭が将来の経済的地位を左右しやすいという国際比較の知見です。個人の努力の価値を否定するものではなく、スタート地点の違いを認識し、機会への投資（教育・人脈・地理的移動）を戦略的に考える必要性を示します。The cross-country finding that in more unequal societies, the family you are born into more strongly shapes your economic future. It does not deny the value of effort but shows the need to recognize different starting points and invest strategically in opportunity through education, networks, and geographic mobility.
グレート・ギャツビー・カーブは、経済学者 Miles Corak の研究に基づき、2012年に米大統領経済諮問委員会の Alan Krueger が命名した図で、横軸に所得格差（ジニ係数）、縦軸に世代間所得弾力性（親の所得が子の所得をどれだけ説明するか）を取ると、正の相関が見られることを示します。デンマークやノルウェーなど格差が小さい国では移動性が高く、米国、英国、イタリア、ブラジルなど格差の大きい国では親の経済状況が子の将来をより強く規定します。Raj Chetty らの研究は、米国内でも地域によって移動性が大きく異なり、学校の質、地域の分断、家族の安定性などが影響することを明らかにしました。この知見は「成功は努力次第」という物語を修正し、機会の構造を直視することを求めます。個人にとっては、自分がどのようなスタート地点にいるかを認識し、教育、職業ネットワーク、機会の多い地域への移動といった「機会への投資」の重要性を理解する助けになります。同時に、成功した人が自らの成功を努力だけに帰さず、他者の機会を広げる責任を考える出発点にもなります。The Great Gatsby curve, based on research by economist Miles Corak and named in 2012 by Alan Krueger of the US Council of Economic Advisers, plots income inequality (the Gini coefficient) against intergenerational income elasticity, the degree to which parents' income predicts children's income, and reveals a positive correlation. Low-inequality countries such as Denmark and Norway show high mobility, while high-inequality countries such as the United States, United Kingdom, Italy, and Brazil show parental circumstances shaping children's futures more strongly. Raj Chetty and colleagues found that mobility also varies sharply across regions within the United States, influenced by school quality, segregation, and family stability. The finding corrects the narrative that success depends on effort alone and asks us to face the structure of opportunity. For individuals it helps in recognizing one's starting point and understanding the importance of investing in opportunity through education, professional networks, and moving to places with more of it. It is also a starting point for successful people to consider their responsibility to widen opportunity for others rather than attributing everything to their own effort.
構造を強調しすぎると「どうせ生まれで決まる」という無力感を招き、個人の行動を止めてしまいます。逆に努力だけを強調すると、恵まれない環境の人を不当に責める文化を生みます。また、相関は因果を意味せず、格差と移動性の関係のメカニズムについては研究者の間でも議論が続いています。Overemphasizing structure breeds a sense that birth decides everything, which stops individual action. Overemphasizing effort creates a culture that unfairly blames those from disadvantaged backgrounds. Correlation is not causation, and researchers continue to debate the mechanisms linking inequality and mobility.
構造と主体性を両立させる姿勢が現実的です。自分に影響できる範囲（スキル、居住地、人間関係、情報源）に集中し、影響できない範囲は認識にとどめます。恵まれた側にいる場合は、メンタリングや奨学金支援など、他者の機会構造を変える行動を成功の定義に組み込むことが、社会全体の移動性を高めます。A realistic stance holds structure and agency together. Focus on what you can influence, skills, where you live, relationships, and information sources, and simply acknowledge what you cannot. If you are on the advantaged side, build actions that change others' opportunity structure, such as mentoring or scholarship support, into your definition of success; this raises mobility for society as a whole.