diff --git a/.github/test_durations.py b/.github/test_durations.py
index 9f46bbbf36..b5d7e9e954 100644
--- a/.github/test_durations.py
+++ b/.github/test_durations.py
@@ -28,8 +28,9 @@
 LINE = re.compile(
     r"(\d{4}-\d\d-\d\dT\d\d:\d\d:\d\d(?:\.\d+)?)Z "
     r"\[(gw\d+)\] \[\s*\d+%\] (?:PASSED|FAILED|SKIPPED|XFAIL|XPASS|ERROR) (.+?)"
-    # The job's once-a-minute memory report can land on the same line.
-    r"(?: memory: \d+ MB used, \d+ MB available)? *$"
+    # The job's once-a-minute memory report can land on the same line. It
+    # counts MiB; logs from before November 2026 label it MB.
+    r"(?: memory: \d+ Mi?B used, \d+ Mi?B available)? *$"
 )
 # pytest-xdist logs this once its workers are up; a worker's first test is
 # timed from here.
diff --git a/.github/workflows/test-suite.yaml b/.github/workflows/test-suite.yaml
index 2d780c7c27..c834d29968 100644
--- a/.github/workflows/test-suite.yaml
+++ b/.github/workflows/test-suite.yaml
@@ -4,10 +4,10 @@
 # publish. All three run the same jobs in the same locked environment.
 #
 # Jobs: the YAML policy tests (which also list every Python test), the Python
-# tests split over seven runners, and Result, which fails unless every listed
+# tests split over eight runners, and Result, which fails unless every listed
 # Python test ran in exactly one shard and passed, apart from the outcomes
 # accepted in .github/test_outcome_allowlist.toml. A caller that names its job
-# Test gets the checks "Test / YAML", "Test / Python K/7" and "Test / Result";
+# Test gets the checks "Test / YAML", "Test / Python K/8" and "Test / Result";
 # "Test / Result" is the one to require.
 #
 # Runners. These jobs, and the check jobs that pull requests, merge queue
@@ -143,7 +143,8 @@ jobs:
           retention-days: 7
 
   Python:
-    # Shard K of N runs the tests whose node id hashes to K (--shard in
+    # The last shard runs the tests that need the dataset. Each other shard K
+    # of N runs the remaining tests whose node id hashes to K (--shard in
     # policyengine_uk/tests/conftest.py), so each test is in exactly one
     # shard. N is the number of jobs this matrix makes: to add a shard, add
     # a number to the list.
@@ -182,6 +183,18 @@ jobs:
     # cancelled shard 1/6 with its tests at 99% (run 41191216150, first
     # attempt). With seven, the listed slow tests come to about 115 minutes
     # of worker time per shard instead of 134.
+    #
+    # Eight, not seven, for memory: the eighth runs the tests that need the
+    # dataset, with one worker, so only one simulation of the dataset runs at
+    # a time, and the other seven run none of them. In merge queue run
+    # 42212587066 the five shards that built the fixture in
+    # test_aggregate_impact_certified.py peaked at 14.2 to 15.3 GiB, and the
+    # two without it at 10.9 and 12.6 GiB. On a merge of 28 pull requests with
+    # those tests on all seven shards, runs 42218280596 and 42218280615 lost
+    # eight of their 14 shard jobs within minutes at 15.1 to 15.4 GiB, and
+    # shard 6/7 of the first lost its runner at 15.2 GiB 51 minutes in, with
+    # test_latest_data_smoke.py running. With the certified tests on one shard
+    # of seven, run 42231098419 lost that shard at 15.2 GiB.
     name: Python ${{ matrix.shard }}/${{ strategy.job-total }}
     if: ${{ !inputs.skip }}
     runs-on: ${{ vars.CI_RUNNER_ARM != '' && (vars.CI_RUNNER_EVENTS == '' || contains(format(',{0},', vars.CI_RUNNER_EVENTS), format(',{0},', github.event_name))) && vars.CI_RUNNER_ARM || 'ubuntu-24.04-arm' }}
@@ -203,7 +216,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        shard: [1, 2, 3, 4, 5, 6, 7]
+        shard: [1, 2, 3, 4, 5, 6, 7, 8]
     steps:
       - name: Checkout repo
         uses: actions/checkout@v6
@@ -230,6 +243,7 @@ jobs:
           POLICYENGINE_UK_REQUIRE_TEST_DATA: ${{ inputs.require-data && '1' || '' }}
           SHARD: ${{ matrix.shard }}/${{ strategy.job-total }}
           OUTCOMES: outcomes-${{ matrix.shard }}.jsonl
+          WORKERS: ${{ matrix.shard == strategy.job-total && 1 || 4 }}
           # Measure coverage with sys.monitoring instead of the C trace
           # function: the same lines are reported, at less cost per line.
           COVERAGE_CORE: sysmon
@@ -238,9 +252,10 @@ jobs:
             export HUGGING_FACE_TOKEN="$HF_TOKEN_VALUE"
           fi
           # Log memory each minute, so a runner lost to memory pressure
-          # ("The runner has received a shutdown signal") shows it.
+          # ("The runner has received a shutdown signal") shows it. free -m
+          # counts MiB.
           (while sleep 60; do
-            free -m | awk 'NR == 2 { print "memory: " $3 " MB used, " $7 " MB available" }'
+            free -m | awk 'NR == 2 { print "memory: " $3 " MiB used, " $7 " MiB available" }'
           done) &
           trap 'kill $! 2>/dev/null' EXIT
           coverage=()
@@ -250,14 +265,15 @@ jobs:
           # .github/pytest_outcome_log.py records each test's outcome for
           # Result. xfail_strict makes an xfail marker without strict= fail
           # when its test passes, so a fixed bug cannot hide behind it.
-          # Four pytest-xdist workers, one per core. Their memory grows with
-          # each test they run (#2330): with three shards they peaked at
-          # 15.6 GB of the runner's 16 GB (run 38156967136).
+          # Four pytest-xdist workers, one per core, and one on the last shard.
+          # Their memory grows with each test they run (#2330): with three
+          # shards they peaked at 15.3 GiB of the 15.6 GiB the runner reports
+          # as used and available (run 38156967136).
           PYTHONPATH="$GITHUB_WORKSPACE/.github" pytest "$TESTS" \
             --rootdir "$ROOTDIR" -c pyproject.toml -p no:cacheprovider \
             -p pytest_outcome_log --outcome-log="$OUTCOMES" \
             -o xfail_strict=true --maxfail=0 -v \
-            -n 4 --dist worksteal --shard "$SHARD" "${coverage[@]}"
+            -n "$WORKERS" --dist worksteal --shard "$SHARD" "${coverage[@]}"
       - name: Upload the test outcomes
         if: ${{ !cancelled() }}
         uses: actions/upload-artifact@v7
diff --git a/Makefile b/Makefile
index 982d241540..6e8b2e0d24 100644
--- a/Makefile
+++ b/Makefile
@@ -24,7 +24,7 @@ test-yaml:
 
 # Every Python test, serially. To spread them over four cores add
 # PYTEST_ARGS="-n 4 --dist worksteal" (pytest-xdist); to run what one CI
-# shard runs, add "--shard K/7" (policyengine_uk/tests/conftest.py). CI runs
+# shard runs, add "--shard K/8" (policyengine_uk/tests/conftest.py). CI runs
 # these tests through .github/workflows/test-suite.yaml, in the locked
 # environment (uv sync --frozen --extra dev), and also checks each test's
 # outcome against .github/test_outcome_allowlist.toml.
diff --git a/changelog.d/data-tests-own-shard.changed.md b/changelog.d/data-tests-own-shard.changed.md
new file mode 100644
index 0000000000..dce89ae3db
--- /dev/null
+++ b/changelog.d/data-tests-own-shard.changed.md
@@ -0,0 +1 @@
+Run the tests that need the dataset in their own CI shard, with one worker, so the other seven shards no longer build simulations of the whole dataset.
diff --git a/docs/engineering/skills/testing.md b/docs/engineering/skills/testing.md
index 2659f448a9..dd22873a20 100644
--- a/docs/engineering/skills/testing.md
+++ b/docs/engineering/skills/testing.md
@@ -86,15 +86,17 @@ the same suite,
 tree; a release tests the wheel it is about to publish, installed on its own.
 
 The suite runs the YAML policy tests in one job and splits the Python tests
-over seven runners. Each runner runs one shard:
+over eight runners. Each runner runs one shard:
 
 ```bash
-pytest policyengine_uk/tests -n 4 --dist worksteal --shard K/7 -o xfail_strict=true
+pytest policyengine_uk/tests -n 4 --dist worksteal --shard K/8 -o xfail_strict=true
 ```
 
-`--shard K/N` is defined in `policyengine_uk/tests/conftest.py`. It keeps the
-tests whose node id hashes to shard K of N, so every test is in exactly one
-shard, including a test added later. Each shard records every test's outcome
+`--shard K/N` is defined in `policyengine_uk/tests/conftest.py`. Shard N of N
+keeps the tests with the `microsimulation` marker, which need the dataset, and
+CI runs it with one worker. Every other shard keeps the remaining tests whose
+node id hashes to it, so every test is in exactly one shard, including a test
+added later. Each shard records every test's outcome
 with `.github/pytest_outcome_log.py`. The final job, `Test / Result`, runs
 `.github/check_test_shards.py`. It fails unless every collected test ran in
 exactly one shard and passed. The exceptions are outcomes accepted in
diff --git a/policyengine_uk/tests/code_health/test_ci_test_shards.py b/policyengine_uk/tests/code_health/test_ci_test_shards.py
index 0193a5b67f..459a9e9da0 100644
--- a/policyengine_uk/tests/code_health/test_ci_test_shards.py
+++ b/policyengine_uk/tests/code_health/test_ci_test_shards.py
@@ -40,6 +40,9 @@
     the least loaded shard, whatever order the table lists them in, so no
     shard's listed load exceeds another's by more than the longest test; the
     table parses and each entry names a test function that exists.
+13. With two or more shards, the last runs exactly the tests that need the
+    dataset, and ``shard_of`` over one shard fewer places the others. The
+    workflow numbers its shards from 1 to N and gives the last one one worker.
 """
 
 import ast
@@ -245,6 +248,56 @@ def test_a_missing_table_leaves_every_test_to_the_hash(conftest, tmp_path):
     assert conftest.read_shard_durations(tmp_path / "absent.toml") == {}
 
 
+# Invariant 13: the last shard runs the tests that need the dataset.
+
+
+class _CollectedTest:
+    """What item_shard reads from a pytest item."""
+
+    def __init__(self, nodeid, needs_data):
+        self.nodeid = nodeid
+        self.needs_data = needs_data
+
+    def get_closest_marker(self, name):
+        return object() if self.needs_data and name == "microsimulation" else None
+
+
+@PROPERTY_SETTINGS
+@given(
+    collection=st.dictionaries(nodeids, st.booleans(), max_size=40),
+    shards=st.integers(2, 8),
+)
+def test_the_last_shard_runs_exactly_the_tests_that_need_the_dataset(
+    conftest, collection, shards
+):
+    for nodeid, needs_data in collection.items():
+        shard = conftest.item_shard(_CollectedTest(nodeid, needs_data), shards)
+        if needs_data:
+            assert shard == shards
+        else:
+            assert shard == conftest.shard_of(nodeid, shards - 1) < shards
+
+
+@PROPERTY_SETTINGS
+@given(nodeid=nodeids, needs_data=st.booleans())
+def test_one_shard_runs_every_test(conftest, nodeid, needs_data):
+    assert conftest.item_shard(_CollectedTest(nodeid, needs_data), 1) == 1
+
+
+def test_the_workflow_gives_the_last_shard_one_worker():
+    import yaml
+
+    workflow = GITHUB_DIR / "workflows" / "test-suite.yaml"
+    job = yaml.safe_load(workflow.read_text(encoding="utf-8"))["jobs"]["Python"]
+    shards = job["strategy"]["matrix"]["shard"]
+    assert shards == list(range(1, len(shards) + 1))
+    [step] = [step for step in job["steps"] if step.get("name") == "Run the tests"]
+    assert step["env"]["WORKERS"] == (
+        "${{ matrix.shard == strategy.job-total && 1 || 4 }}"
+    )
+    assert '-n "$WORKERS"' in step["run"]
+
+
 # Invariant 4: the collection listing.
 
 
@@ -545,6 +598,15 @@ def test_never_runs():
     raise AssertionError
 """
 
+SAMPLE_DATA_TEST = """
+import pytest
+
+
+@pytest.mark.microsimulation
+def test_needs_the_dataset():
+    pass
+"""
+
 FAILING_SUITE = """
 import pytest
 
@@ -608,6 +670,11 @@ def test_passes():
 nodeid = "suite/test_skipped_module.py"
 outcome = "collect-skipped"
 why = "sample"
+
+[[allow]]
+nodeid = "suite/test_latest_data_smoke.py::test_needs_the_dataset"
+outcome = "skipped"
+why = "sample"
 """
 
 
@@ -728,19 +795,32 @@ def test_a_skipped_subtest_is_not_hidden_by_its_tests_pass(tmp_path):
 
 @pytest.mark.parametrize("xdist", [(), ("-n", "2", "--dist", "worksteal")])
 def test_real_pytest_shards_pass_the_check_only_when_allowed(tmp_path, xdist):
-    _suite(tmp_path, test_sample=SAMPLE_SUITE, test_skipped_module=SKIPPED_MODULE)
+    # conftest.py verifies no dataset for a test in this file (UNPINNED_BY_DESIGN),
+    # so the run downloads nothing.
+    _suite(
+        tmp_path,
+        test_sample=SAMPLE_SUITE,
+        test_skipped_module=SKIPPED_MODULE,
+        test_latest_data_smoke=SAMPLE_DATA_TEST,
+    )
     listing = _pytest(tmp_path, "suite", "--collect-only", "-q")
     assert listing.returncode == 0, listing.stdout + listing.stderr
     collected = tmp_path / "collected.txt"
     collected.write_text(listing.stdout, encoding="utf-8")
-    assert len(checker.read_collected(listing.stdout)) == 43
+    assert len(checker.read_collected(listing.stdout)) == 44
 
     logs = _run_shards(tmp_path, 3, *xdist)
     sizes = [
         sum(not r.is_collector for r in checker.read_outcomes(log.read_text()))
         for log in logs
     ]
-    assert sum(sizes) == 43 and all(sizes)
+    assert sum(sizes) == 44 and all(sizes)
+    # The last shard runs the test that needs the dataset and nothing else.
+    assert [
+        r.nodeid
+        for r in checker.read_outcomes(logs[-1].read_text())
+        if not r.is_collector
+    ] == ["suite/test_latest_data_smoke.py::test_needs_the_dataset"]
     allowlist = tmp_path / "allow.toml"
     allowlist.write_text(SAMPLE_ALLOWLIST, encoding="utf-8")
 
diff --git a/policyengine_uk/tests/conftest.py b/policyengine_uk/tests/conftest.py
index d945afd3e5..3511547f5e 100644
--- a/policyengine_uk/tests/conftest.py
+++ b/policyengine_uk/tests/conftest.py
@@ -175,7 +175,7 @@ def pytest_report_header(config):
     ]
     shard = config.getoption("shard", default=None)
     if shard is not None:
-        lines.append(f"shard: {shard[0]} of {shard[1]}, chosen by node id")
+        lines.append(f"shard: {shard[0]} of {shard[1]}, by marker and node id")
     return lines
 
 
@@ -193,12 +193,17 @@ def cloned_uk_tax_benefit_system():
 
 
 # CI splits the suite over several runners with ``--shard K/N``. The shard of a
-# test is a function of its node id alone (and of the checked-in table below),
-# so the shards partition whatever is collected: every test runs in exactly
-# one of them, including a test added later. The Test job checks that on each
-# run (.github/check_test_shards.py).
+# test is a function of its marker and node id alone (and of the checked-in
+# table below), so the shards partition whatever is collected: every test runs
+# in exactly one of them, including a test added later. The Test job checks that
+# on each run (.github/check_test_shards.py).
 #
-# Most tests are placed by a hash of their node id. A hash spreads thousands
+# The last shard runs the tests that need the dataset, which build simulations
+# of all of it, and the other shards share the rest. CI gives the last shard
+# one worker, so only one of those simulations runs at a time
+# (.github/workflows/test-suite.yaml has the measurements).
+#
+# Most other tests are placed by a hash of their node id. A hash spreads thousands
 # of short tests evenly, but not a few long ones: on 24 October 2026 one
 # property test took 22 minutes, and by chance it and several others of 4 to
 # 7 minutes hashed to shard 2 of 5, which then took 57 minutes on average
@@ -257,6 +262,17 @@ def shard_of(nodeid: str, shards: int) -> int:
     return int.from_bytes(digest[:8], "big") % shards + 1
 
 
+def item_shard(item, shards: int) -> int:
+    """The shard, from 1 to ``shards``, that runs a collected test.
+
+    The last of two or more shards runs the tests that need the dataset, and
+    ``shard_of`` places the others on the remaining shards.
+    """
+    if shards == 1:
+        return 1
+    return shards if needs_data(item) else shard_of(item.nodeid, shards - 1)
+
+
 def parse_shard(value: str) -> tuple[int, int]:
     """Parse ``K/N`` into ``(K, N)``, requiring 1 <= K <= N."""
     match = re.fullmatch(r"([0-9]+)/([0-9]+)", value)
@@ -286,7 +302,7 @@ def pytest_collection_modifyitems(config, items):
         this_shard, shards = shard
         selected, deselected = [], []
         for item in items:
-            if shard_of(item.nodeid, shards) == this_shard:
+            if item_shard(item, shards) == this_shard:
                 selected.append(item)
             else:
                 deselected.append(item)
diff --git a/policyengine_uk/tests/shard_durations.toml b/policyengine_uk/tests/shard_durations.toml
index 5e04dd9d37..d4d48e2694 100644
--- a/policyengine_uk/tests/shard_durations.toml
+++ b/policyengine_uk/tests/shard_durations.toml
@@ -11,7 +11,8 @@
 # test_ci_test_shards.py fails if an entry names a test that no longer
 # exists, so a pull request that renames or removes a listed test should
 # rename or delete its line here. Regenerate when a shard drifts well above
-# the others.
+# the others. The last shard runs the tests that need the dataset, so this
+# table leaves them out: regenerate it from the other shards' logs.
 [seconds]
 "policyengine_uk/tests/test_capital_share_components.py::test_capital_matches_the_original_lists" = 1299
 "policyengine_uk/tests/test_statutory_pension_edges.py::test_nics_cap_preserves_aa_inputs_and_charge_with_fixed_ordinary_tax[2029]" = 761
@@ -21,14 +22,10 @@
 "policyengine_uk/tests/test_dated_reform_routes.py::test_routes_agree_on_start_stop_keys" = 392
 "policyengine_uk/tests/test_reform_representations.py::test_parametric_reform_representations_agree" = 368
 "policyengine_uk/tests/test_tax_credits_pension_credit_passport_properties.py::test_results_do_not_depend_on_request_order" = 340
-"policyengine_uk/tests/aggregate_impact/test_aggregate_impact_certified.py::test_accounting_identities_and_closure_hold" = 338
-"policyengine_uk/tests/aggregate_impact/test_aggregate_impact_certified.py::test_household_detail_is_complete" = 338
-"policyengine_uk/tests/aggregate_impact/test_aggregate_impact_certified.py::test_every_tax_component_is_counted_exactly_once" = 333
 "policyengine_uk/tests/test_childcare_entitlement_floor_properties.py::test_more_hours_used_never_lowers_childcare_support" = 330
 "policyengine_uk/tests/test_pension_credit_earnings_disregard_properties.py::test_statute_bounds_differential_and_monotonicity" = 330
 "policyengine_uk/tests/test_tax_credits_pension_credit_passport_properties.py::test_without_awards_pension_credit_alone_decides_the_passport" = 320
 "policyengine_uk/tests/test_brma_region_default.py::test_brma_with_sparse_regions_follows_the_rule_and_keeps_regions" = 302
-"policyengine_uk/tests/aggregate_impact/test_aggregate_impact_certified.py::test_declared_double_counts_are_still_double_counted_by_the_model" = 301
 "policyengine_uk/tests/test_housing_benefit_universal_credit_passport_properties.py::test_universal_credit_limb_dates" = 296
 "policyengine_uk/tests/test_from_reform_modifier.py::test_sequence_modifier_matches_apply_with_repeated_and_reordered_writes[True]" = 288
 "policyengine_uk/tests/test_pension_credit_child_amount_tax_credit_properties.py::test_results_do_not_depend_on_request_order" = 286
@@ -359,8 +356,6 @@
 "policyengine_uk/tests/test_housing_benefit_savings_credit_only_properties.py::test_income_follows_the_route_for_the_award" = 50
 "policyengine_uk/tests/test_housing_benefit_specified_accommodation_disregard_properties.py::test_income_support_disregards_all_earnings" = 49
 "policyengine_uk/tests/test_pension_age_severe_disability_premium_properties.py::test_net_income_does_not_fall_where_guarantee_credit_ends" = 49
-"policyengine_uk/tests/microsimulation/test_reform_impacts.py::test_reform_fiscal_impacts[Raise personal allowance by ~800GBP/year]" = 49
-"policyengine_uk/tests/microsimulation/test_reform_impacts.py::test_reform_fiscal_impacts[Raise basic rate by 1pp]" = 49
 "policyengine_uk/tests/test_scenario_sum_timing.py::test_a_simulation_runs_each_part_once_at_its_own_time" = 48
 "policyengine_uk/tests/test_uc_statutory_pay_properties.py::test_statutory_pay_counts_as_wages_and_earned_income_adds_up" = 48
 "policyengine_uk/tests/test_uc_work_related_groups_properties.py::test_thresholds_follow_the_group_and_expected_hours" = 48
@@ -380,7 +375,6 @@
 "policyengine_uk/tests/test_variable_module_release.py::test_dead_systems_modules_are_released_while_a_test_runs" = 47
 "policyengine_uk/tests/test_housing_benefit_pension_age_cohorts.py::test_council_tax_reduction_splits_only_in_england" = 47
 "policyengine_uk/tests/test_capital_gains_tax_components.py::TestEqualisationReforms::test_main_rate_reform_leaves_the_other_schedules_at_current_law" = 47
-"policyengine_uk/tests/microsimulation/test_reform_impacts.py::test_reform_fiscal_impacts[Raise Class 1 main employee NICs rate to 10%]" = 47
 "policyengine_uk/tests/test_uc_property_capital.py::test_financial_allocation_conserves_pool_with_reports_and_complete_overrides" = 46
 "policyengine_uk/tests/test_housing_benefit_specified_accommodation_disregard_properties.py::test_no_earner_has_no_para_18_amount" = 46
 "policyengine_uk/tests/test_housing_benefit_earnings_disregard_properties.py::test_disregard_lowers_applicable_income_by_no_more_than_earnings" = 46
@@ -405,8 +399,6 @@
 "policyengine_uk/tests/test_pension_credit_war_pension_properties.py::test_guarantee_credit_does_not_rise_with_an_afcs_payment" = 44
 "policyengine_uk/tests/test_ni_class_2.py::test_ni_class_2_properties" = 44
 "policyengine_uk/tests/test_statutory_paternity_pay_income_tax_properties.py::test_statutory_paternity_pay_is_treated_as_statutory_sick_pay" = 44
-"policyengine_uk/tests/microsimulation/test_salary_sacrifice_cap_reform.py::test_salary_sacrifice_cap_revenue_impact" = 44
-"policyengine_uk/tests/microsimulation/test_state_pension_reform.py::test_relative_state_pension_reform_affects_budget" = 44
 "policyengine_uk/tests/test_uc_childcare_work_condition_properties.py::test_condition_matches_the_regulation_32_reference" = 43
 "policyengine_uk/tests/test_housing_benefit_specified_accommodation_disregard_properties.py::test_bounds" = 43
 "policyengine_uk/tests/test_housing_benefit_universal_credit_passport_properties.py::test_universal_credit_passport_ignores_income_and_capital" = 43
@@ -421,11 +413,8 @@
 "policyengine_uk/tests/test_pension_annual_allowance_properties.py::test_charge_matches_band_by_band_reference" = 43
 "policyengine_uk/tests/test_severe_disability_premium_properties.py::test_premium_matches_independent_oracle_and_range" = 43
 "policyengine_uk/tests/test_uc_company_owner_properties.py::test_property_company_gives_no_earnings" = 43
-"policyengine_uk/tests/test_scenario_baseline_parameters.py::test_before_load_spending_scenario_constructs_on_the_dataset" = 43
 "policyengine_uk/tests/test_uc_disabled_child_addition_properties.py::test_exact_award_categories_and_blindness_select_one_tier" = 42
 "policyengine_uk/tests/test_lha_published_rates.py::test_northern_ireland_maxima_and_minimum_change_only_northern_ireland" = 42
-"policyengine_uk/tests/aggregate_impact/test_aggregate_impact_certified.py::test_head_totals_agree_with_the_model_weighted_sums" = 42
-"policyengine_uk/tests/microsimulation/test_reform_impacts.py::test_reform_fiscal_impacts[Raise higher rate by 1pp]" = 42
 "policyengine_uk/tests/test_salary_sacrifice_ni_only.py::test_explicit_actual_return_matches_actual_pay_and_member_inputs[employee_pension_contributions]" = 42
 "policyengine_uk/tests/test_dataframe_dataset.py::test_an_exported_frame_gives_the_results_of_its_dataset[default export]" = 42
 "policyengine_uk/tests/test_ni_class_4_profits_properties.py::test_losses_carry_forward_over_many_years" = 42
@@ -462,12 +451,10 @@
 "policyengine_uk/tests/test_uc_childcare_work_condition_properties.py::test_a_couple_both_in_paid_work_always_meets_the_condition" = 37
 "policyengine_uk/tests/test_state_pension_components.py::test_add_on_follows_september_cpi_and_nothing_else_changes" = 37
 "policyengine_uk/tests/test_property_income_band_base_properties.py::test_non_savings_taxable_income_is_the_rest_after_allowances" = 37
-"policyengine_uk/tests/aggregate_impact/test_aggregate_impact_certified.py::test_spending_never_rises_by_more_than_is_added_except_known_defects" = 37
 "policyengine_uk/tests/test_rent_of_sharers_boarders_and_lodgers_properties.py::test_non_dependants" = 37
 "policyengine_uk/tests/test_statutory_paternity_pay_income_tax_properties.py::test_statutory_paternity_pay_is_taxed_as_wages" = 36
 "policyengine_uk/tests/test_trading_loss_properties.py::test_class_4_profits_net_of_the_loss_balance" = 36
 "policyengine_uk/tests/test_dataframe_dataset.py::test_an_exported_frame_gives_the_results_of_its_dataset[export of every stored value]" = 36
-"policyengine_uk/tests/microsimulation/test_salary_sacrifice_cap_reform.py::test_decile_impact_negative_for_higher_earners" = 36
 "policyengine_uk/tests/test_dated_reform_routes.py::test_a_fresh_process_agrees_with_a_warm_one" = 36
 "policyengine_uk/tests/test_statutory_pension_edges.py::test_trade_losses_do_not_leak_nics_reclassification_into_aa[DB-2030]" = 35
 "policyengine_uk/tests/test_trading_loss_properties.py::test_relief_is_the_loss_within_net_income_and_the_cap" = 35
@@ -484,19 +471,14 @@
 "policyengine_uk/tests/test_council_tax_reduction_child_benefit_properties.py::test_pensioner_ctr_is_invariant_to_actual_child_benefit_claim" = 33
 "policyengine_uk/tests/test_child_benefit_charge_rounding_properties.py::test_simulated_charge_matches_the_statute" = 33
 "policyengine_uk/tests/code_health/test_cached_arrays_not_written_in_place.py::test_branching_runs_with_read_only_cache[labour_supply_responses]" = 33
-"policyengine_uk/tests/microsimulation/test_salary_sacrifice_cap_reform.py::test_income_tax_impact" = 33
 "policyengine_uk/tests/test_disable_simulated_benefits_winter_heating.py::test_reported_winter_heating_is_conserved" = 33
-"policyengine_uk/tests/microsimulation/test_reform_impacts.py::test_reform_fiscal_impacts[Reduce Universal Credit taper rate to 20%]" = 33
 "policyengine_uk/tests/test_capital_gains_tax_components.py::TestEqualisationReforms::test_setting_every_schedule_taxes_every_gain_alike" = 32
 "policyengine_uk/tests/test_triple_lock_statutory_inputs.py::test_policy_levers_apply_from_the_april_of_the_year_they_name" = 32
 "policyengine_uk/tests/test_disable_simulated_benefits_winter_heating.py::test_reported_winter_heating_follows_each_years_country" = 32
 "policyengine_uk/tests/test_uc_health_element_freeze.py::test_lifting_the_freeze_reaches_a_simulated_new_claimant" = 31
-"policyengine_uk/tests/microsimulation/test_reform_impacts.py::test_reform_fiscal_impacts[Raise child benefit by 25GBP/week per additional child]" = 31
 "policyengine_uk/tests/test_state_pension_age.py::test_extracted_household_keeps_its_birthday" = 30
 "policyengine_uk/tests/test_benefit_cap_specified_benefits_properties.py::test_an_element_a_reform_gives_is_decided_by_its_value[uc_carer_element]" = 30
-"policyengine_uk/tests/microsimulation/test_reform_impacts.py::test_reform_fiscal_impacts[Raise VAT standard rate by 2pp]" = 30
 "policyengine_uk/tests/test_benefit_cap_specified_benefits_properties.py::test_an_element_a_reform_gives_is_decided_by_its_value[uc_LCWRA_element]" = 29
-"policyengine_uk/tests/microsimulation/test_reform_impacts.py::test_reform_fiscal_impacts[Raise additional rate by 3pp]" = 28
 "policyengine_uk/tests/test_dated_reform_routes.py::test_a_scenario_keeps_its_modifiers_parameters_and_its_parameter_changes[False]" = 28
 "policyengine_uk/tests/test_targeted_childcare_guarantee_credit_properties.py::test_known_families_detect_the_earlier_routes" = 27
 "policyengine_uk/tests/test_data_built_imputations.py::test_imputations_do_not_depend_on_total_weight" = 27
@@ -521,7 +503,6 @@
 "policyengine_uk/tests/test_from_reform_modifier.py::test_modifier_matches_scenario_apply_on_built_parameters" = 24
 "policyengine_uk/tests/test_legacy_award_readers_properties.py::test_an_outside_adults_work_keeps_their_non_dependant_deduction" = 24
 "policyengine_uk/tests/test_savings_credit_only_receipt_properties.py::test_stopping_pension_credit_payments_ends_savings_credit_only_receipt" = 24
-"policyengine_uk/tests/microsimulation/test_salary_sacrifice_cap_reform.py::test_ni_increases_with_reform" = 24
 "policyengine_uk/tests/test_dataframe_dataset.py::test_a_reform_on_an_exported_frame_gives_the_results_of_its_dataset" = 24
 "policyengine_uk/tests/test_capital_gains_responses.py::test_realisations_fall_when_rates_rise" = 24
 "policyengine_uk/tests/test_lha_freeze.py::test_great_britain_lha_maxima_and_minimum_leave_northern_ireland_unchanged" = 24
@@ -561,10 +542,8 @@
 "policyengine_uk/tests/test_marginal_rates_hold_behavioural_responses.py::test_marginal_rates_hold_the_labour_supply_response[marginal_tax_rate_on_capital_gains-22000-0-changes0]" = 21
 "policyengine_uk/tests/test_claims_all_entitled_benefits.py::TestPerBenefitUnit::test_reporters_of_any_of_the_seven_are_false" = 21
 "policyengine_uk/tests/test_marginal_rates_hold_behavioural_responses.py::test_marginal_tax_rate_holds_the_capital_gains_response[13000]" = 21
-"policyengine_uk/tests/test_latest_data_smoke.py::test_universal_credit_aggregate_in_range" = 21
 "policyengine_uk/tests/test_capital_gains_response_default.py::test_pay_rise_branches_hold_the_realisation_response" = 21
 "policyengine_uk/tests/code_health/test_cached_arrays_not_written_in_place.py::test_branching_runs_with_read_only_cache[capital_gains_responses]" = 21
-"policyengine_uk/tests/microsimulation/test_state_pension_reform.py::test_basic_state_pension_responds_to_reform" = 21
 "policyengine_uk/tests/test_council_tax_reduction_pensioner_earnings_disregard_properties.py::test_disregard_is_the_statutory_weekly_sum_in_every_year" = 21
 "policyengine_uk/tests/test_marginal_rates_hold_behavioural_responses.py::test_marginal_rates_hold_the_labour_supply_response[marginal_tax_rate_wrt_employer_cost-0-10000-changes2]" = 21
 "policyengine_uk/tests/test_disable_simulated_benefits_winter_heating.py::test_reform_sets_reported_benefits[Simulation]" = 21