English to German Bus/Financial Insurance assessing the sustainability of pension plans with actuarial balances

In meinem Text geht es um die Beurteilung der finanziellen Nachhaltigkeit von Rentensystemen der sozialen Sicherheit mithilfe von versicherungsmathematischen Bilanzen, bzw. um die Frage, nach welchen Methoden diese Bilanzen erstellt werden müssen, um aussagekräftig zu sein.
Es werden verschiedene Methoden zur Erstellung untersucht, wobei eine wesentliche Unterscheidung die Zugrundelegung von 'open groups' bzw. 'closed groups' ist. Hier die Definitionen:

For fully funded systems, the accrued liabilities are assumed to be funded in advance; therefore, balance sheets under *closed groups (i.e. that take into account current contributors only)* with or without future accruals are appropriate for such plans. In contrast, pay-as-you-go (PAYG) and partially funded systems represent social contracts where, in any given year, current contributors allow the use of their contributions to pay current beneficiaries’ benefits. As a result, such social contracts create a claim for current and past contributors to contributions of future contributors. The proper assessment of the financial sustainability of a social security PAYG or partially funded system by means of its balance sheet should take these claims into account. The traditional closed group methodologies do not reflect these claims since only current participants are considered. In comparison, the *open group approach accounts explicitly for these claims by considering the benefits and contributions of both current and future plan participants* (OSFI, 2012).

Ich habe bislang von offenen bzw. geschlossenen Gruppen geschrieben, aber vielleicht gibt es einen Fachbegriff?