Abstract: This article analyses the mechanisms establishing time consistency of constitutions. It explains why shorter and more locked constitutions are more likely to be time consistent (change less) and that long constitutions are more time inconsistent (change more, despite locking). Empirical evidence from all of the democratic countries in the world indicates that the length and locking of constitutions are not independent criteria, and that their combination leads to less time consistency. To address this inter-relationship, a measure of time inconsistency (a combination of locking and amendment rate) is developed and it is demonstrated that it is connected with the length of constitutions. The article shows how time inconsistency is incompatible with theories of ‘constitutional amendment culture’ not only at the theoretical level, but also empirically. Finally, the article proves that the empirical finding that the length of constitutions is related to lower per capita income and higher corruption are not only in agreement with time inconsistency arguments, but this also extends beyond OECD countries to all democracies.