Pietu Niinimäki has officiated 138 matches on record, averaging 3.8 cards and 4.1 fouls per game — a balanced official. A player is dismissed roughly once every 7 games, and the spot is pointed to 0.33 times per match. Home teams win 44% of matches under him, drawing 27% and losing 29%. Most active in the Ykkösliiga (77 matches). 42% of his bookings come after the 75th minute, with the first card around the 38'. He cards more than 22% of Ykkösliiga 2025 referees.