infra/docs/plans/2026-05-28-wealth-projections-plan.md

Wealth Net-Worth Projections — Implementation Plan

Pairs with 2026-05-28-wealth-projections-design.md. Built 2026-06-01.

Goal: Add a collapsed "Projections" row to the wealth Grafana dashboard (UID wealth) with a 30-year multi-scenario net-worth projection, driven by pure SQL over the (now LOCF-fixed) dav_corrected view.

Architecture: Edit infra/stacks/monitoring/modules/monitoring/dashboards/wealth.json via a one-off Python builder (reliable JSON construction). Add 6 template variables + 1 collapsed row + projection panels. Deploy via targeted scripts/tg apply of the dashboard ConfigMap; Grafana sidecar reloads.

Tech stack: Grafana 11.2 (schemaVersion 39), Postgres datasource wealth-pg.

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Validated inputs (live, 2026-06-01)

• nw0 (net worth today) = £1,163,011 — latest-per-account SUM(total_value).
• auto monthly contribution run-rate = £15,755/mo (trailing 12 complete months ÷ 12).
• Historical return = trailing-3-full-year geometric mean of per-year Modified-Dietz returns = 10.43%.
• FV math verified: n=0 = nw0 for every line; base@30y ≈ £27.3M, high ≈ £52.8M.

GOTCHA (why not "all-time CAGR")

The complete-days filter (all 7 accounts present) only reaches back to 2026-01-30 because the newest account is recent — so an "all-time CAGR over complete days" annualised a ~4-month window into a nonsense 83.71%. And the true all-time geomean (17.5%) is dominated by 2021's small-base +86% year and would dwarf a 30y chart. Decision (user, 2026-06-01): use the trailing-3-full-year geomean (~10.4%) — represents "current returns", chart-sane. Per-year MD returns reuse the existing "Yearly investment return %" methodology (each year uses its own first/last obs; no all-complete requirement).

Template variables (add to templating.list — dashboard has none today)

name	type	default	hide
rate_low	textbox	4	0
rate_base	textbox	7	0
rate_high	textbox	10	0
monthly_contribution	textbox	auto	0
horizon_years	textbox	30	0
hist_cagr	query (datasource wealth-pg)	computed	2 (hidden)

hist_cagr query:

WITH active_count AS (SELECT COUNT(*) n FROM accounts), mc AS (SELECT MAX(valuation_date) d FROM (SELECT valuation_date, COUNT(*) c FROM dav_corrected GROUP BY valuation_date) x WHERE c >= (SELECT n FROM active_count)), yearly AS (SELECT EXTRACT(YEAR FROM valuation_date)::int yr, valuation_date, SUM(total_value) nw, SUM(net_contribution) contrib FROM dav_corrected WHERE valuation_date <= (SELECT d FROM mc) GROUP BY valuation_date), ep AS (SELECT yr, (array_agg(nw ORDER BY valuation_date))[1] nw_s, (array_agg(nw ORDER BY valuation_date DESC))[1] nw_e, (array_agg(contrib ORDER BY valuation_date))[1] c_s, (array_agg(contrib ORDER BY valuation_date DESC))[1] c_e, COUNT(*) days FROM yearly GROUP BY yr), r3 AS (SELECT (nw_e-nw_s-(c_e-c_s))/NULLIF(nw_s+0.5*(c_e-c_s),0) ret FROM ep WHERE (nw_s+0.5*(c_e-c_s))>0 AND days>=300 ORDER BY yr DESC LIMIT 3) SELECT ROUND((exp(avg(ln(1+ret)))-1)*100,2) FROM r3

Panels (new collapsed row "📈 Projections", at bottom, y=200)

1. Text panel "How to view" with two dashboard links: [Show projection range](?from=now-3y&to=now%2B30y) / [Reset](?from=now-180d&to=now). (h=3,w=24)
2. Stat row (h=4): NW today · Historical return (trailing 3y) · Monthly contribution (auto) · Projected NW @ base in $horizon_yearsy.
3. Timeseries "Net worth — $horizon_years-year projection" (h=12,w=24), two targets (A wide projection, B actual 3y tail). Field overrides: actual = solid; Low/Base/High/Historical = dashed; "Base, no new contributions" = dotted.

Panel 3 Target A (wide projection) — column aliases embed the rate for legends

WITH active_count AS (SELECT COUNT(*) n FROM accounts), mc AS (SELECT MAX(valuation_date) d FROM (SELECT valuation_date, COUNT(*) c FROM dav_corrected GROUP BY valuation_date) x WHERE c >= (SELECT n FROM active_count)), latest AS (SELECT DISTINCT ON (account_id) account_id, total_value, net_contribution FROM dav_corrected WHERE valuation_date <= (SELECT d FROM mc) ORDER BY account_id, valuation_date DESC), agg AS (SELECT SUM(total_value) nw0, SUM(net_contribution) c_now FROM latest), ago AS (SELECT SUM(x.nc) c_ago FROM latest l LEFT JOIN LATERAL (SELECT net_contribution nc FROM dav_corrected d WHERE d.account_id=l.account_id AND d.valuation_date <= (SELECT d FROM mc) - INTERVAL '12 months' ORDER BY d.valuation_date DESC LIMIT 1) x ON true), params AS (SELECT (SELECT nw0 FROM agg) nw0, CASE WHEN '$monthly_contribution'='auto' THEN ((SELECT c_now FROM agg)-(SELECT c_ago FROM ago))/12.0 ELSE '$monthly_contribution'::numeric END cm, ($rate_low::float)/100 rl, ($rate_base::float)/100 rb, ($rate_high::float)/100 rh, ($hist_cagr::float)/100 rhist), m AS (SELECT generate_series(0, ${horizon_years}*12) n) SELECT (now() + (m.n || ' months')::interval) AS "time", round((nw0*power(1+(power(1+rl,1/12.0)-1),m.n) + cm*((power(1+(power(1+rl,1/12.0)-1),m.n)-1)/NULLIF(power(1+rl,1/12.0)-1,0)))::numeric,0) AS "Low ($rate_low%)", round((nw0*power(1+(power(1+rb,1/12.0)-1),m.n) + cm*((power(1+(power(1+rb,1/12.0)-1),m.n)-1)/NULLIF(power(1+rb,1/12.0)-1,0)))::numeric,0) AS "Base ($rate_base%)", round((nw0*power(1+(power(1+rb,1/12.0)-1),m.n))::numeric,0) AS "Base, no new contributions", round((nw0*power(1+(power(1+rh,1/12.0)-1),m.n) + cm*((power(1+(power(1+rh,1/12.0)-1),m.n)-1)/NULLIF(power(1+rh,1/12.0)-1,0)))::numeric,0) AS "High ($rate_high%)", round((nw0*power(1+(power(1+rhist,1/12.0)-1),m.n) + cm*((power(1+(power(1+rhist,1/12.0)-1),m.n)-1)/NULLIF(power(1+rhist,1/12.0)-1,0)))::numeric,0) AS "Historical ($hist_cagr%)" FROM m, params

Panel 3 Target B (actual history, 3y tail)

WITH active_count AS (SELECT COUNT(*) n FROM accounts), mc AS (SELECT MAX(valuation_date) d FROM (SELECT valuation_date, COUNT(*) c FROM dav_corrected GROUP BY valuation_date) x WHERE c >= (SELECT n FROM active_count)) SELECT valuation_date::timestamp AS "time", SUM(total_value) AS "Net worth (actual)" FROM dav_corrected WHERE valuation_date <= (SELECT d FROM mc) AND valuation_date >= now()::date - INTERVAL '3 years' GROUP BY valuation_date ORDER BY valuation_date

Stat SQL

• NW today: WITH latest AS (SELECT DISTINCT ON (account_id) total_value FROM dav_corrected d JOIN accounts a ON a.id=d.account_id ORDER BY account_id, valuation_date DESC) SELECT SUM(total_value) FROM latest
• Historical return %: SELECT $hist_cagr::float
• Monthly contribution (auto): the agg/ago run-rate ((c_now)-(c_ago))/12.0
• Projected @ base: Target-A base formula evaluated at n = $horizon_years*12

Build / deploy / verify

1. Build: one-off Python script /tmp/build_projection.py (outside repo) loads wealth.json, appends the 6 vars + row + panels, fixes the "Net pay vs market gain — per month" panel (#3) to month-end deltas, writes back.
2. Validate: python -c json.load; unique panel ids; spot-run Target A/B against live wealth-pg.
3. Deploy: scripts/tg apply -target=...grafana_dashboards["wealth.json"] (targeted — monitoring stack has unrelated pre-existing drift).
4. Verify: ConfigMap carries new content; user expands the row, clicks "Show projection range", confirms 5 projected lines flow from today + the actual tail; toggles $monthly_contribution=0 to see the contribution gap.

Scope notes

• Skip the optional "projected NW by year" table (YAGNI; add later if wanted).
• #3 ("Net pay vs market gain — per month") aligned to month-end deltas in the same build for monthly-market-gain consistency.
• Fidelity growth-timing cosmetic = NOT in scope (user deferred 2026-06-01).