Figure 1 - The distribution of registrations is shown for Statphys 23 (red triangles), up to the main deadline for abstract submission (T^*), and for the EP2DS 17 conference (blue circles), rescaled with respect to the total number of participants; the solid line corresponds to a simple model in which the pressure to register is inversely proportional to the time left before the deadline.

The level of agreement between the data for the two conferences and the model suggests that there is a simple universal behaviour in response to a deadline. The inset shows the distribution in time of payment of the conference fee (credit-card payments only): the distribution is more peaked towards the deadline because, although registration is reversible, payment is irreversible. The simple model (dashed line) is not accurate in this case, and it is necessary to include an exponential utility function (solid line).