stats: index neighbour growth from 2016 (after mergers), clearer tariff and levy labels

src/routes/stats/gouda/+page.svelte

@@ -42,9 +42,12 @@
 	const social = $derived(last('cbs:stock:social:GM0513'));
 	const levy = $derived(last('cbs:levy:total:GM0513'));
 
-	// Index every ring municipality's monthly population to 100 in Jan 2002 so sizes compare.
-	const indexed = (p: StatPoint[]): StatPoint[] =>
-		p.length ? p.map(([d, v]) => [d, Math.round((v / p[0][1]) * 1000) / 10]) : [];
+	// Index every ring municipality's monthly population to 100 in Jan 2016 so sizes compare.
+	// CBS reports historical borders, so start after the last merger (Krimpenerwaard, 2015).
+	const indexed = (all: StatPoint[]): StatPoint[] => {
+		const p = all.filter(([d]) => d >= '2016-01-01');
+		return p.map(([d, v]) => [d, Math.round((v / p[0][1]) * 1000) / 10] as StatPoint);
+	};
 	const levyRank = $derived(
 		RING.map((r) => ({ r, p: last(`cbs:levy:total:${r}`) }))
 			.filter((x) => x.p)
@@ -164,8 +167,8 @@
 			)}
 	/>
 	<StatChart
-		title="Growth since 2002, Gouda and its neighbours"
-		subtitle="monthly population, January 2002 = 100"
+		title="Growth since 2016, Gouda and its neighbours"
+		subtitle="monthly population, January 2016 = 100"
 		sources={['cbs']}
 		attributions={a}
 		option={(t) =>
@@ -293,7 +296,7 @@
 	/>
 	<StatChart
 		title="Municipal levies"
-		subtitle={`€ per multi-person household (property tax, sewer, waste) · ${period(levy?.[0], 'A')}`}
+		subtitle={`total municipal housing charges, € per multi-person household · ${period(levy?.[0], 'A')}`}
 		sources={['cbs']}
 		attributions={a}
 		option={(t) => barRankOption(t, levyRank, { decimals: 0, unit: '€', color: '#64748b' })}