Game Play Analysis IV

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SELECT ROUND( COUNT(A1.player_id) / (SELECT COUNT(DISTINCT A3.player_id) FROM Activity A3) , 2) AS fraction FROM Activity A1 WHERE (A1.player_id, DATE_SUB(A1.event_date, INTERVAL 1 DAY)) IN ( SELECT A2.player_id, MIN(A2.event_date) FROM Activity A2 GROUP BY A2.player_id );