Why governing parties change their platforms more frequently than those in opposition

Following an election, are parties that enter government more likely to alter their electoral platform than parties in opposition? Gijs Schumacher, Marc van de Wardt, Barbara Vis and Michael Baggesen Klitgaard present findings from data on party programmes going back to 1945. Their research indicates that, contrary to expectations, parties in government are more likely to alter their programme than parties in opposition, but that this effect depends on the extent to which parties aspire to hold office in the next election.