Concept Architecture
Concept
Theoretically, Attachment Point is the predefined financial threshold at which stop-loss insurance or reinsurance coverage begins to reimburse losses. It represents the level of retained risk that the insured entity must absorb before excess-loss protection becomes effective. The concept is fundamental to actuarial science, insurance economics and healthcare financing because it determines the allocation of financial risk between the primary payer and the insurer or reinsurer.
Mathematically, the Attachment Point is represented as a fixed monetary amount or as a percentage of expected claims. It defines the trigger for excess-loss reimbursement, whereby payments commence only when eligible claims exceed the specified threshold. The attachment point therefore establishes the boundary between retained losses and insured losses within an excess-of-loss framework.
In practice, attachment points are determined using actuarial analysis of historical claims experience, projected healthcare utilisation and the organisation's risk tolerance. Individual stop-loss policies typically specify a per-person attachment point, whereas aggregate stop-loss policies define an attachment point based on expected annual claims. The selected threshold influences insurance premiums, retained financial risk and budget predictability.
Purpose
Used to define the level of financial risk retained by a healthcare payer before stop-loss or reinsurance coverage applies, allocate risk between contracting parties, determine insurance premiums and protect organisations against catastrophic healthcare expenditure.
Mathematical Formulae
Primary Formula
Excess Loss = max(0, C ? A)
where:
- C = eligible claims
- A = attachment point
Supporting Formulae
Aggregate Attachment Point = Expected Claims ? Attachment Percentage
Retained Loss = min(C, A)
Related Mathematical Methods
- Excess-of-loss modelling
- Stop-loss insurance modelling
- Aggregate claims modelling
- Actuarial risk analysis
- Expected value analysis
Example
A self-funded employer expects annual healthcare claims of �8,000,000 and purchases aggregate stop-loss insurance with an attachment point of 125%.
Attachment Point = �8,000,000 ? 1.25 = �10,000,000
Actual eligible claims total �10,600,000.
Excess Loss = max(0, �10,600,000 ? �10,000,000)
= �600,000
The stop-loss insurer reimburses �600,000, while the employer retains the first �10,000,000 of claims.
Excel Implementation
| Function | Example Formula | Health Economics Application |
|---|---|---|
| PRODUCT | =B2*B3 | Calculates the attachment point from expected claims and attachment percentage. |
| MAX | =MAX(0,B5-B6) | Calculates reimbursable excess losses. |
| MIN | =MIN(B5,B6) | Calculates retained claims below the attachment point. |
| IF | =IF(B5>B6,B5-B6,0) | Determines whether stop-loss coverage is triggered. |
VBA (Optional)
A VBA routine can automatically compare accumulated claims with the attachment point and calculate reimbursable excess losses for stop-loss reporting.
Sources
- Dickson DCM, Hardy MR, Waters HR. Actuarial Mathematics for Life Contingent Risks.
- Klugman SA, Panjer HH, Willmot GE. Loss Models: From Data to Decisions.
- Society of Actuaries. Health Section Educational Materials.
- ISPOR Good Practice Reports.
- Drummond MF, Sculpher MJ, Claxton K, Stoddart GL, Torrance GW. Methods for the Economic Evaluation of Health Care Programmes.
Related Concepts (2)
Library
Publications
1
The Economics of Health and Health Care — Folland, Goodman, Stano & Danagoulian, 9th Edition ed., 2024 (Routledge)
The market-leading general health economics textbook, giving comprehensive coverage of health economics through core economic themes and balancing theory, empirical evidence and public policy. The ninth edition adds chapters on health disparities and pandemic economics.
BookView source →
Frequently Asked Questions (6)
What is an attachment point?
The specific threshold at which a stop-loss or reinsurance policy begins covering costs, with the insured responsible for costs below it.
Source: Cutler DM, Zeckhauser RJ. The anatomy of health insurance. In: Culyer AJ, Newhouse JP, eds. Handbook of Health Economics. Vol 1A. Elsevier; 2000:563-643. doi:10.1016/S1574-0064(00)80170-5.
At what threshold does coverage begin under an attachment point?
An attachment point is the threshold at which a stop-loss or reinsurance policy begins to cover costs. Below it, the insured party, such as a self-insured employer, bears the costs itself; above it, the stop-loss policy takes over. It matters because it sets how much risk the insured retains before protection kicks in: a low attachment point means more is covered but the policy costs more, a high one the reverse. The point where reinsurance starts paying is what it marks. Cutler and Zeckhauser (2000) set out the anatomy of insurance.
Source: Cutler & Zeckhauser 2000
How does an attachment point work?
An attachment point works by setting a threshold below which the insured bears the costs and above which the stop-loss or reinsurance policy pays, so coverage begins once costs reach the point. So an attachment point works by dividing responsibility at the threshold, which is why it is a specific level, since the insured pays up to the point and the policy covers the excess, and setting the attachment point determines where the stop-loss or reinsurance coverage begins, with the insured responsible for costs below it.
Source: Cutler & Zeckhauser 2000
Why does an attachment point matter?
An attachment point matters because it determines how much cost the insured bears before reinsurance begins, so a higher attachment point means the insured retains more risk and a lower one means the policy covers more. So the attachment point matters for risk sharing, which is why its level is important, since it sets how much the insured bears before coverage starts, and the attachment point matters because it fixes the threshold at which the stop-loss or reinsurance policy begins to pay, shaping how much risk the insured retains.
Source: Cutler & Zeckhauser 2000
What does the insured bear below the attachment point?
Below the attachment point, the insured bears the costs themselves, since the stop-loss or reinsurance policy only begins covering costs once they reach the threshold. So the insured bears costs below the attachment point, which is why it is a threshold, since coverage starts only above the point, and below the attachment point the insured is responsible for the costs, with the stop-loss or reinsurance policy covering the costs that exceed the point once the threshold is reached.
Source: Cutler & Zeckhauser 2000
How does an attachment point relate to stop-loss coverage?
An attachment point relates to stop-loss coverage as the threshold that triggers it: stop-loss coverage protects against high costs, and the attachment point is the level at which that coverage begins. So the attachment point defines where stop-loss begins, which is why they are connected, since stop-loss pays above the point and the insured bears costs below, and the attachment point sets the threshold for stop-loss coverage, determining the point at which the policy starts to cover the costs above it.
Source: Cutler & Zeckhauser 2000
Trust Record
Verified by Dr Darrin Baines
British health economist
Professional identity: darrinbaines.org
Verification date: 9 Jan 2026
Content version: 1.0.0
Canonical Identity
- Persistent URI
- https://healtheconomics.wiki/concept/attachment-point
- Term code
- HS-HP-HI-014
Stable URI · Machine-readable · Resolvable · CC BY 4.0