Answer :World population is now of the order of 7 billion i.e. 700 crore people. Assuming five people make on family -140 crore families will be there. Assuming each family takes at least 2 calendars - 280 crore calendars for families Another 10% towards companies, corporates, Government - +28 crore Totally 308 crore calendars is estimated to be manufactured in the world based on the assumptions made.
Answer :According to Wikipedia - world population will reach 7 billion by october 2011. Imagining that four people make one family then 175 crore families will be there and imagining one famiy takes 3 calendars the toal number required will be 525 crore calendars. This figure will take into account the calendars used in corporates, governments and other places.