Vrijwillig verloop: formule en voorbeeld.

WITH avg_hc AS (
  SELECT AVG(n) AS n
  FROM (
    SELECT m, COUNT(e.employee_id) AS n
    FROM generate_series(DATE '2025-01-01', DATE '2025-12-01', interval '1 month') AS m
    JOIN employees e ON e.hire_date <= m AND (e.termination_date IS NULL OR e.termination_date > m)
    GROUP BY m
  ) s
)
SELECT COUNT(*) FILTER (WHERE e.termination_reason = 'voluntary') AS voluntary_leavers,
       COUNT(*) AS all_leavers,
       ROUND(100.0 * COUNT(*) FILTER (WHERE e.termination_reason = 'voluntary') / NULLIF(MAX(h.n), 0), 1) AS voluntary_turnover_pct
FROM employees e
CROSS JOIN avg_hc h
WHERE e.termination_date >= DATE '2025-01-01' AND e.termination_date < DATE '2026-01-01';

Voluntary Leavers =
CALCULATE ( COUNTROWS ( Employees ), Employees[TerminationReason] = "voluntary", USERELATIONSHIP ( Employees[TerminationDate], 'Date'[Date] ) )
Voluntary Turnover % =
DIVIDE (
    [Voluntary Leavers],
    AVERAGEX ( VALUES ( 'Date'[YearMonth] ), VAR d = CALCULATE ( MAX ( 'Date'[Date] ) ) RETURN COUNTROWS ( FILTER ( ALL ( Employees ), Employees[HireDate] <= d && ( ISBLANK ( Employees[TerminationDate] ) || Employees[TerminationDate] > d ) ) ) )
)