Data from over 4000 recent association football (soccer) matches from the main English competitions show clear evidence that the rate of scoring goals changes over the course of a match. This rate tends to increase over the game but is also influenced by the current score. We develop a model for a soccer match that incorporates parameters for both the attacking and the defensive strength of a team, home advantage, the current score and the time left to play. This model treats the number of goals scored by the two teams as interacting birth processes and shows a satisfactory fit to the data. We also investigate football cliches and find evidence that contradicts the cliche that a team is more vulnerable just after it has scored a goal.