I have read in an article about this year's UCI World Championships:
There are six riders per team, meaning a smaller size when compared to, say, nine for last July’s team time trial in Nice for the Tour de France. Also the time taken is usually on the fifth rider but for the worlds, with the smaller teams, the time will be taken on the fourth rider.
Are there some official rules about which rider's time determines team's result in team time trial? Or is it decided by organizer of each individual race?