The number of members, predominantly women, some engaged only in constant prayer, others working as teachers, health workers and missionaries, fell 94,790 to 945,210.
Of the total, 753,400 members were women, while 191,810 were men, including 136,171 priests and 532 permanent deacons.
The figures were published next to a report of Pope Benedict XVI's meeting with nuns, monks and priests from many countries gathered in St Peter's Basilica in Rome last weekend.
The BBC's David Willey in the Italian capital says the accelerating downward trend must have caused concern to the Pope.
The Roman Catholic Church has an aging and diminishing number of parish and diocesan clergy and this latest fall is quite dramatic, our correspondent says.
The number of Catholic nuns worldwide declined by about a quarter during the reign of Pope John Paul, and this further drop shows that new recruits are failing to replace those nuns who die, or decide to abandon their vows, he adds.
Is this for real? The old orders are getting grey and dying off along with the rest of the post-war boom. Welcome to global demographics.