From caffeine-free diet drinks to oversize envelopes, a lot is missing this month from the shelves of Paris shops - if they're open at all.

But the penury isn't what it once was when, come Aug. 1, the French would pack up and flee the capital in droves.Many still do, of course, but statistics show that the French - for whom "les conges annuels" or, paid vacation, is something of a national institution - are taking shorter summer holidays.

Gone are the days when Parisians would shutter their apartments and bundle off to the seaside, mountains or country home for four straight weeks - or more, if they could afford it.

"The French are staggering their vacations more than in the past," said Marie-Anne Brignol, a spokeswoman for the French Office of Tourism. "They go away for shorter periods of time in the summer, but they're taking more vacations during the year."

Don't expect the French to relinquish a single moment of the paid holidays they've enjoyed since 1936, when the government granted all salaried workers the right to two weeks' paid leave.

Today, they get a minimum of five weeks off - the most in Europe - and can take four weeks consecutively.

According to a report by the Tourism Ministry, two out of three French went on holiday last year - 57 percent of them during July or August.

But with the growing awareness that closing down in August may be counterproductive, many employers are encouraging workers to stay on the job in summer and take their holidays off-season.

The French media, for example, get an extra week off if the time is taken between Oct. 1 and May 31.

Yet, long-established vacation habits are slow to change. Paris shopkeepers who remain open complain they run out of some goods because their suppliers and dealers are on vacation.