Chris Giles explains in his Holy Week column for The Financial Times:
As any Christian will tell you, Jesus was crucified on Good Friday and the faithful celebrate his resurrection on Easter Sunday.My emphasis. Thanks to grapeshisha for emailing the link.
Hang on a minute, say economists.
Sure, the spike in church attendance on Easter Sunday results, in part, from the special pleasure people derive from marking Easter in church. But the supply-side product enhancements many churches offer in holy week - special choral and flower arrangements and the increased networking opportunities that come with a full house - also help to tilt the cost-benefit balance towards Easter Sunday attendance.
As a result, religious observance falls below average in the weeks following Easter as the semi-regular worshippers who shifted their attendance to holy week drop away.