Methodology · v2.10

DTSBoard Tenure Balance

Average director tenure on {legal_name}'s board (years). Use a TIER fallback — do NOT return absent unless BOTH tiers fail. TIER 1 (preferred): compute the STRICT ARITHMETIC AVERAGE across ALL sitting directors using their `board_service_start_year` from the latest proxy statement / DEF 14A / Companies House officer records / national business registry visura / BoardEx. Formula: `avg = sum(current_year - start_year) / count(directors)`. Example: 8 directors with start years 2000, 2009, 2003, 2008, 2015, 2010, 2014, 2011 and current_year=2024 → (24+15+21+16+9+14+10+13)/8 = 15.25. State the explicit `(t1+...+tN)/N` in _reasoning. TIER 2 (fallback when per-director start years are NOT individually disclosed): use the average board/director tenure figure REPORTED by a reputable governance data source (Simply Wall St, BoardEx, MSCI, ISS, Spencer Stuart board index) and cite the exact page — e.g. "experienced board (8.3 years average tenure)". Emit that reported figure as the value. Only return absent{reason:"not_disclosed"} if NEITHER a per-director list NOR a reputable reported average can be found. NO post-hoc adjustment, NO "conservative round-down". Return exact_numerical{value: <avg_tenure_years>, unit: "years", source_urls: [...]}. Server applies board_tenure_sweet_spot (inverted-U: 3y → ~65, 5y → ~85, 7y → ~95 sweet spot, 10y → ~90, 15y → ~68, 18y → ~55, 20y+ → entrenchment floor 40-48) — DO NOT compute any 0-100 score, DO NOT round. Just emit the average tenure in years; the server applies the governance curve.