/*highest percentage of high salaries*/
SELECT educationlevel, ROUND(high_salary*1.0/low_salary, 1) AS high_to_low_ratio FROM
(SELECT educationlevel,
    SUM (CASE WHEN salarylevel = '>50K' THEN 1 ELSE 0 END) as high_salary,
    SUM (CASE WHEN salarylevel = '<=50K' THEN 1 ELSE 0 END) as low_salary
FROM person
GROUP BY  educationlevel) groups 
ORDER BY 2 DESC;