I have long held a theory that you can tell a country's general income level (and maybe even its Gini coefficient) by what's on its roads and pavements.

Look around. Do you mostly see shiny, top-of-the-range cars, sporting air-con and hi-fi? Or do you spot cars that have seen better days, maybe missing many frills like window-wipers and headlights?

Are there swarms of small motorbikes? How many people are riding them? Just one or two? Or mum, dad, and several children? And what are the bikes being used for? Have they been kitted out with all manner of ingenious devices for the transporting of wide loads? (If so, they're likely to be carrying - well, anything really, from pigs to wardrobes.)

Public transport is also an income indicator. Are there shiny sky-trains, metros, and air-conditioned buses? Or are there reeking buses of vast antiquity, supplemented by an army of motorcycle taxis, tuk-tuks and communal vans?

And how many bicycles are there? Are people pedalling their own? Or are they loading themselves, their children and their goods into the little capsule of one of many pedicab arrangements?

And how many carts do you see on the roads? Maybe they're little carts pushed by people. Maybe they're big carts pulled by horses or buffalos.

And what about the pedestrian? Is he/she striding along on a regular pavement, confident of protection from traffic lights and regulations? Or is she/he dicing it out on the road along with the traffic, the pavement having been commandeered for displaying goods for sale, or for parking motorbikes, or for dumping large piles of whatever can't be accommodated elsewhere?

Here are some examples, out of many.

Aggregate all this -- I would hypothesize -- and you get a pretty good idea of the income level of the particular country, and of the size of the gap between its richest citizens and its poorest.

Now, I'm not saying the richer end of life is always better. Far from it. In door-to-door terms, you can often get around more efficiently and comfortably in the informal transport at the poorer end of the spectrum than in the formal transport at the richer end (and it somehow seems to be beyond the wit of urban planners to combine the best of both worlds).

But the streetscape/income correlation seemed pretty watertight.

Until I came to Taiwan.

Taiwan's odd geopolitical status means you can't get comparisons from the statistics you normally consult. But the World Bank attests that Taiwan is a high-income country. And a government report claims that Taiwan would weigh in at 22nd on the United Nations Development Programme's Human Development Index, if the usual methodology were applied. In Asia, that would put it behind only Japan and South Korea.

And what doesn't fit, in Taiwan's case, is that there are millions of scooters...

Everything else fits. The cars are modern. The public transport is superb. In two weeks I've yet to see a traffic jam. In Taipei at least, the pavements are walkable, and the traffic respects the rules (not quite so true, mind you, in Tainan or Hualien). Most of the pedal-powered bits of equipment are piloted by lycra-clad fitness enthusiasts. And there's nothing on four legs.

But people still scoot. Avidly.

Intriguing.