The Reserve Walk

The booked claims reserve has fallen since the previous valuation. Payments explain much of the reduction, but the closing balance is higher than we expected a year ago.

A reserve walk helps explain what changed. Closing the reserve for prior-period claims before adding the new period makes their development easier to assess. An expected closing marker shows whether the remaining reserve is in line with the previous valuation's expectations.

The Decision Question

What changed the booked reserve since the previous valuation, and how much of that movement was expected?

Management needs to understand whether the change reflects claims being paid, new claims entering the reserve, or revisions to the cost of existing claims.

Default practice

A reserve walk reconciles the opening reserve to the closing reserve. The waterfall shows payments as a reduction, the unpaid reserve for newly incurred claims as an addition, and changes in estimates for earlier claims as separate movements.

In this illustrative example, the booked reserve falls from R100 million to R94 million. Payments of R44 million reduce the balance, while new-year unpaid claims add R25 million. An experience-driven revision of R8 million and assumption changes of R5 million increase the reserve for earlier claims.

The chart gives management an exact reconciliation and makes the main drivers visible.

Where the Default Breaks Down

Combining prior-period development with new-period reserves makes the result for earlier claims harder to read. Without an expectation benchmark, the R6 million fall in the total gives little reassurance.

Payments reduce the unpaid balance even when estimated total claims costs are rising. New-period reserves also reflect exposure. The direction of the total movement alone can misdirect the discussion.

Suggested upgrade

Complete the bridge for prior-period claims first. Start with the opening reserve, deduct expected payments and any payments above expectation, then show the experience revision and assumption changes. Insert a closing reserve subtotal for prior-period claims before adding the closing reserve for new-period claims.

Expected payments take the opening R100 million to R58 million. Extra payments of R2 million, an experience revision of R8 million and assumption changes of R5 million bring prior-period closing to R69 million. Adding R25 million for new-period claims takes the total to R94 million.

Separating anticipated movement from other changes is an established actuarial approach. The upgrade adds a prior-period closing subtotal, with a reference marker at its R58 million expected balance. The R25 million new-period addition is the unpaid reserve at closing; payments on those claims are already reflected in that amount.

What This Immediately Reveals

The prior-period reserve closes at R69 million against an expected R58 million. The R11 million difference is visible before any reserve for new-period claims is added.

R44 million was paid on prior-period claims, but their estimated total cost increased by R13 million through experience revisions and assumption changes. That strengthening more than offset the R2 million of payments above expectation. Higher payments alone do not establish favourable claims experience; they may reflect settlement timing or higher claim costs.

Management can investigate the experience revision and assumption change separately from the new-period reserve. The total falls by R6 million but closes R11 million above expectation, because the new-period R25 million matches its expectation here.

Trade-offs and risks

The expected prior-period closing reserve must use the previous valuation's basis and payment expectations. An expectation reconstructed using closing assumptions would weaken the comparison. Assess the new-period reserve against its own exposure and claims expectations; the prior-period marker does not evaluate that addition.

Keep movements mutually exclusive and define periods by when claims were incurred. The opening reserve and prior-period payments must cover the same claims. Expected payments already represent expected run-off; a second deduction would double-count it. Newly reported claims from earlier periods may already be covered by opening IBNR and belong in prior-period development. Add the new period's unpaid closing reserve, rather than its full ultimate cost.

Experience and assumption effects can interact. Document the calculation order and show material method changes separately. Keep gross or net treatment consistent. If the booked reserve includes discounting, risk margins or management adjustments, reconcile those movements too. This example excludes them.

The R11 million gap from expected prior-period closing is a balance-sheet comparison. In this undiscounted example, the one-year claims development result is R100 million less R44 million paid and R69 million remaining: an adverse R13 million. The payment difference explains why this differs from the R11 million gap. Aggregate movements may conceal differences across classes and accident years.

Decision Boundary

Use this when…	Don’t use this when…
You need to reconcile the booked opening and closing reserves.	You need a standalone judgement on reserve adequacy or the appropriate booking.
You need to assess prior-period development separately from the new-period reserve.	Payments and reserves cannot be separated consistently by the period in which claims were incurred.
You have a credible previous-valuation expectation for the prior-period closing reserve.	The expectation has been reconstructed using closing assumptions.
You need to identify changes for investigation.	You need to read the gap from expected closing directly as the claims development result or profit impact.