From fec4793ae66c6c0f0880f7d61672222e071949a1 Mon Sep 17 00:00:00 2001 From: Vahid Ahmadi Date: Mon, 20 Apr 2026 10:58:56 +0100 Subject: [PATCH] Set Marriage Allowance take-up rate to HMRC outturn (#368) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The placeholder 1.0 (100%) overstated Marriage Allowance take-up. HMRC outturn shows ~2.1m claimants of ~4.2m eligible couples (~50%), which means microsimulation overstates the program cost by ~£500m/year. Set the parameter to 0.5 with a House of Commons Library citation. Companion change in PolicyEngine/policyengine-uk#1636. Source issue: PolicyEngine/policyengine-uk#623. Co-Authored-By: Claude Opus 4.7 (1M context) --- changelog.d/368.md | 1 + .../parameters/take_up/marriage_allowance.yaml | 7 +++++-- 2 files changed, 6 insertions(+), 2 deletions(-) create mode 100644 changelog.d/368.md diff --git a/changelog.d/368.md b/changelog.d/368.md new file mode 100644 index 000000000..3d6318809 --- /dev/null +++ b/changelog.d/368.md @@ -0,0 +1 @@ +- Set Marriage Allowance take-up rate to 0.5 (HMRC outturn ~2.1m claimants of ~4.2m eligible couples) instead of the placeholder 1.0, so microsimulation no longer overstates Marriage Allowance cost by ~£500m/year. diff --git a/policyengine_uk_data/parameters/take_up/marriage_allowance.yaml b/policyengine_uk_data/parameters/take_up/marriage_allowance.yaml index ff528bba7..603c4b4bd 100644 --- a/policyengine_uk_data/parameters/take_up/marriage_allowance.yaml +++ b/policyengine_uk_data/parameters/take_up/marriage_allowance.yaml @@ -1,6 +1,9 @@ -description: Percentage of eligible couples who claim Marriage Allowance. +description: Share of eligible couples who claim Marriage Allowance. HMRC outturn shows ~2.1m claimants vs ~4.2m eligible (~50% take-up). Read by `datasets/frs.py` to populate `would_claim_marriage_allowance` stochastically per person. metadata: unit: /1 label: Marriage Allowance take-up rate + reference: + - title: House of Commons Library — Income tax allowances for married couples (SN00870) + href: https://commonslibrary.parliament.uk/research-briefings/sn00870/ values: - 2000-01-01: 1 + 2000-01-01: 0.5