French term (edited): propriétaires du capital social de la banque

Not entirely the same as Conor's answer, so CL / confidence levl downgraded in deference.

The full UK title of 'capital social', as every A1 student of (UK) company (US) corporate & partnership law ought to know from their grave study of Topham & Ivamy 'from my day', Gower or Butterworths, is 'Equity Share Capital'.

According to Bourdieu, social capital is the aggregate of the actual or potential resources which are linked to possession of a durable network of more or less institutionalized relationships of mutual acquaintance and recognition – or in other words, to membership in a group– which provides each of its members with the backing of the collectivity-owned capital, a ‘credential’ which entitles them to credit, in the various senses of the word.

The term 'social fund' could be somewhat misleading, since at one time a social fund would be money laid aside for various purposes for the benefits of a community.
In this question the proprietors or the owners of capital seem to be a section of the customers within a bank. The figures state that of the 868 000 customers at the bank, 335 000 of them are shareholders or owners of financial capital. Therefore the bank is owned on a basis of mutuality and it's cooperative.
It's about a fund within a society, which in the question, is a bank or a business company, rather than a society or a community of people or families in a city or a town.


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Note added at 6 hrs (2022-07-26 18:21:39 GMT)
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FR:
On pense à un fond social, ce qui peut être un peu ambigüe. Une fois un fond social serait de l'argent réservé pour les fins du bien d'une communauté.
Dans cette question, les propriétaires d'un capital sont un grand groupe des clients d'une banque. Les chiffres expliquent que des 868 000 clients de la banque, 335 000 parmi eux sont des actionnaires ou des propriétaires d'un capital financier. La banque, donc, est possédée d'une mutualité et elle est coopérative.
Il s'agit d'un fond dedans une société, ce qui, dans cette question est une banque ou une entreprise, plus qu'une société ou une communauté des voisins ou des familles d'une ville.

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Note added at 6 days (2022-08-01 20:06:34 GMT)
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https://www.inclusionlondon.org.uk/training-and-events/infor...
The above reference explains that social investment funds are generally open to voluntary, community and social enterprise organizations.
https://www.investopedia.com/terms/s/socialcapital.asp
The following reference explains that social capital is a positive product of human interaction. It also denotes positive contributions to an organization's success, respect among employees and enhanced company performance.
Both the references are relevant to the source of facts about investments and investors or shareholders in a bank or a social fund of which shareholders are active in an enterprise.

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Note added at 6 days (2022-08-01 20:15:30 GMT)
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FR:
Des fonds d'investissement social sont ouverts aux entreprises volontaires, communitaires et sociales.
Le capital social est un produit positif de l'intéraction humaine. Il s'agit des contributions positives au succès d'une organisation du respect parmi les employés, leurs résultâts ou leurs réussites élévées.
Les deux références sont pertiinentes aux investissments et aux actionnaires d'une banque ou des fonds sociales dont des actionnaires participent dans une entreprise.

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Note added at 6 days (2022-08-01 20:24:16 GMT)
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Dans ce cas, le mot, 'social' décrit un fond qui est à une société ou une entreprise.