A generous soul came up with this -

Subject: Football answer

Hmmm, this is a tricky one, because as any football statistician will tell
you, accurate data is not kept on penalties that are missed. I would imagine
that the proprtion is about 85% scored. (Le Tissier's record is something
like 60 scored from 61 penalties, and I think this is the best ever for a
professional, consistent penalty taker).

Conversion rate has fallen for a number of reasons:

1. Introduction of penalty shoot-outs. If shoot-outs are counted, then the %
falls dramatically because a new player has to take each penalty, meaning
that by the sixth or seventh penalty you have players taking the kicks who
have never taken a penalty in professional football before (e.g. bloody
David Batty who missed against the Argies in World Cup 1998).

2. Goalkeeping has improved more rapidly than striking. This is reflected in
the lower total number of goals scored compared to, say, thirty years ago
(I'd guess about an average of 5 goals a game in the 1950s and about 2.5
goals a game now).

3. The improvements in goalkeeping has meant that strikers have to attempt
to place their penalty kicks more accurately - e.g. top corner of the net
rather than straight down the middle. This reduces the margin of error and
has led to more penalty kicks being off target all together.

4. Penalty-taking is largely psychological. The increased overall pressure
on modern-day footballers makes a miss more likely.

5. Matches tend to be closer these days (1-0, 2-1 rather than 7-3 or 5-2).
This increases the importance of scoring a goal and thus of converting a
penalty and therfore adds to psychological pressure.

6. Goalkeepers - in line with people in general - have got taller over the
generations. The dimensions of the goal remain the same.

Here ends the lesson!

Stylistic note: Penalty kicks are NEVER, NEVER to be referred to as "PKs",
upon pain of death.

Refereeing point: The stats show that teams are about twice as likely to be
awarded a penalty kick at home as away.