See how a pension fund's return turns into your cohort's return.

Under the solidaire premieregeling (SPR), the assets are not partitioned by cohort. The capital is invested as one collective portfolio. The period result is then distributed to participants via predetermined allocation rules (the toedelingsregels), split into a protection return and an excess return, with a solidarity reserve that fills in good years and drains in bad. Cohorts are a calculation overlay on a collective portfolio, never a physical split of the assets. The “conversion” this tool dramatises is allocation (collective → cohorts via rules), not a reconciliation between two parties' cohort sets.

Beschermingsrendement (protection return) is rate-driven and stabilising. In practice it is delivered either directly, via protection portfolios, or indirectly, via the DNB term structure. In this illustrative tool it is abstracted to a single knob; the methods are named for credibility, not separately simulated.

Overrendement (excess return) comes from the return-seeking portfolio. It is the volatile part: drag market return down and the excess stream shrinks toward zero and then turns negative, hammering younger cohorts, who are allocated mostly excess, while pensioners (allocated mostly protection) stay roughly flat. That single frame is the reform's core logic.

The solidariteitsreserve is a buffer. A slice of excess bends into it in good years; it drains back to cushion cohorts, especially retirees, in bad years. Toggle follow the reserve to isolate only those flows, and watch the tank level respond to the scenario.

Going from one-year to five-year cohorts is plain summation: deterministic and lossless. Going the other way has no unique inverse: a five-year band can be split into single years by headcount, by capital, or uniformly, and the choice changes the per-year numbers. The tool refuses to fake it: switching to 1-year stops and asks which rule to apply, then marks the output with an “assumption applied” badge.

For a single illustrative period, the engine computes:

collectiveResult = f(marketReturn, rateChange)        // one collective portfolio
protectionReturn = g(rateChange, protectionLevel)      // rate-driven
excessReturn     = collectiveResult − protectionReturn // residual
reserveDelta     = h(excessReturn, reserveRules)       // fill good / drain bad

for each cohort c:
  creditedReturn[c] = W_protection[c]·protectionReturn
                    + W_excess[c]·(excess − reserveIn)
                    + reserveDraw[c]

W_protection and W_excess are the allocation matrix, the illustrative toedelingsregels. In Build mode you can edit them and the tool checks each row sums to 100%.

• It is an illustrative explainer. The numbers are didactic, not a calculation of any specific fund, and not advice.
• It is not an allocation engine, an ALM tool, or a calculation kernel.
• No real portfolio or participant data ever enters it. The standard is cohort-level; so is this, never participant-level.
• The allocation rules themselves are out of SIVI message scope; they are set by the fund/PUO and shared via policy documents.