In 1950, how many players whose teams have the losing rate less than 20%?
in 1950 refers to year = 1950; losing rate less than 20% refers to divide(lost, add(won, lost)) < 0.2
SELECT COUNT(DISTINCT T1.playerID) FROM players AS T1 INNER JOIN players_teams AS T2 ON T1.playerID = T2.playerID INNER JOIN teams AS T3 ON T3.tmID = T2.tmID WHERE CAST(T3.lost AS REAL) * 100 / (T3.lost + T3.won) < 20