Regular business travellers to the Vietnamese cities of Hanoi and Ho Chi Minh City know it as the 'street corner test'.
Stand on any downtown street corner at any time and glance across the crowds thronging the roads. You will be struck by how many more motorcycles and cars are on the roads compared with last time you visited, and how better dressed the people seem - evidence of Vietnam's expanding consumer classes.
Sharp observers will also note that virtually everyone seems to be young. Amid the mounting international expectation surrounding Vietnam's fast-growing economy and its upcoming entry to the World Trade Organisation, much is made of the country's youthful, dynamic and literate population.
The statistics are worth close scrutiny. As of July, Vietnam's official estimated population stood at 84.4 million. Some 55 per cent are under 25, a reflection of a post-Vietnam-war baby boom and rising living standards over the past 20 years.
What is often overlooked is that such a young population means it is likely to rise by half again before it stabilises at about 120 million as those youngsters settle down and have their own children over the next two decades.
Considerable government and foreign aid work has gone into bringing down the population growth rate over the past 15 years through family planning efforts. It has dropped from more than 2 per cent annual growth to an estimated 1.3 per cent during that time.