The curve doesn't flatten — it accelerates at the top. CUs spending $35.73 per member on marketing grew members 2.34% YoY. CUs spending $7.29 per member grew 1.01% — a 2.3× gap. Most of the gap is between the top quartile and the rest.
All 1,809 federally insured US credit unions with $100M+ in assets, split into quartiles by marketing spend per member (educational & promotional expense, NCUA Account A310, normalized by current member count). Outcome: year-over-year member growth at the latest quarter.
| Marketing spend quartile | Avg (marketing spend quartile) | Range | Credit unions | Avg member growth YoY | Median member growth YoY |
|---|---|---|---|---|---|
| Q1 — lowest spend | $7.29 | $-8.53 – $11.58 | 453 | 1.01% | -0.05% |
| Q2 | $14.51 | $11.59 – $17.75 | 452 | 1.19% | 0.65% |
| Q3 | $21.05 | $17.75 – $24.89 | 452 | 1.11% | 0.99% |
| Q4 — highest spend | $35.73 | $24.89 – $114.87 | 452 | 2.34% | 1.12% |
The hypothesis was that marketing spend would show diminishing returns — a floor below which CUs lose members, an upper bound above which extra spend doesn't buy growth. The 2025 data shows neither. Spend roughly doubles from Q1 ($7.29) to Q2 ($14.51) and growth barely moves (1.01% → 1.19%). Spend roughly doubles again from Q3 to Q4 — and growth more than doubles (1.11% → 2.34%). The curve is convex at the top, not concave.
One interpretation: there's a threshold above which marketing actually starts working — maybe brand-building requires a minimum frequency that single-quartile spending levels don't sustain. The lowest three quartiles all sit in a "passive presence" band; only the top quartile is investing enough to move share. A skeptical interpretation: top-quartile spenders are also growing CUs investing in capacity (call centers, digital, branches) and the marketing line is dragged along by overall investment, not the cause of the growth.
For a CMO board case: if you're below the $25/member threshold and your peer spend is in the top quartile, you're outside the band where the data shows growth happening. Asking for double the marketing budget is the conservative move, not the bold one.
Tudovu Research is published from NCUA call-report data via CU Growth Plan. New analysis each quarter as fresh data lands.
Tudovu's Industry Data Explorer runs this same analysis on a custom peer set — pick the asset tier, state, charter type, or specific competitors and we'll show you where your CU sits in the curve.