Where did you get the 80% figure? The only study I've actually seen on the subject said the keepers pick the correct side around 43% of the time (though that doesn't mean they make a save).
I remember Soccernomics had a whole chapter dedicated to the science and how some clubs approach it - there was a great study about the 2008 CPL Final and how Edwin Van Der Sar figured out Chelsea's PK game and threw Anelka off for the last kick. I might try and dig it out.
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