Percentuali in MySQL

Usa:

SELECT x.company,
       x.year,
       x.annual_total
       x.annual_total / y.total AS percentage
  FROM (SELECT t.company, 
               YEAR(t.date) as year, 
               COUNT( * ) as annual_total
          FROM TABLE t
         WHERE t.company IN ('Medtronic', 'Private')
      GROUP BY YEAR( t.date ) ) x
  JOIN (SELECT t.company,
               COUNT(*) 'total'
          FROM TABLE t
         WHERE t.company IN ('Medtronic', 'Private')
      GROUP BY t.company) y ON y.company = x.company

Se vuoi la percentuale con cifre decimali particolari, usa:

CAST(x.annual_total / y.total AS DECIMAL(2,2)) AS percentage

Verifica che questo dia il conteggio per azienda che ti aspetti:

  SELECT t.company,
         COUNT(*) 'total'
    FROM TABLE t
   WHERE t.company IN ('Medtronic', 'Private')
GROUP BY t.company