By Robert Plummer
Business reporter, BBC News, Sao Paulo
In the chaotic urban sprawl of Brazil's biggest city, the impact of advertising is impossible to ignore.
Massive billboards and skyscraper-sized hoardings line the streets of Sao Paulo, flaunting their wares at motorists caught in the city's ever-present traffic jams.
The choice of products on display sometimes bears witness to the uninhibited nature of Brazilian society.
A remarkable number of ads feature giant images of men and women dressed only in their underwear, while the Brazilian edition of Playboy is publicised with huge posters and cut-outs of the latest centrefold models.
It all adds to the sensory overload of a city that many see as South America's version of the hi-tech cityscape portrayed in the film Blade Runner.
But Sao Paulo's mayor, Gilberto Kassab, takes a dim view of this non-stop barrage of product promotion - much of which, admittedly, has been put up illegally.
He calls it "visual pollution" - and if he has his way, all big public advertising displays will soon be banned from the city.
Mr Kassab has submitted a bill to the Sao Paulo city council that would completely change the urban environment, prohibiting practically all outdoor ads in their present form. "I know the bill is radical, but it's emblematic," he says. "It's controversial, but necessary for the city."
Ordinary Paulistanos are not too keen, fearing that the city's grey concrete would look even greyer without the generous splashes of colour provided by advertising.
Ads in Brazil are often more daring than in other countries
"It would be like New York without Times Square," said one. "No, it would be like eastern Europe before the fall of communism," said another.
Others have dismissed the initiative as a publicity stunt by Mr Kassab, but Brazil's advertising agencies are worried.
"The advertising industry is taking this very seriously," says Paulo Queiroz, media vice-president of DM9DDB, a leading Brazilian agency that has won a series of international awards for its campaigns.
"It's created a lot of insecurity among firms who've invested heavily and long-term in outdoor media, because the contracts are very short-term.
"The outdoor medium is polluted, it's confused, but it's cheap. And it's becoming even cheaper at the moment, because demand is falling.
"The nine-metre by six-metre billboards are losing ground. The gigantic hoardings on the walls of buildings are losing ground, because no-one's going to invest a lot of money without knowing whether it will all still be legal in two, three or four months' time."
Of course, impressive as they are, billboards are just one element in Brazil's flourishing advertising landscape.
Television remains by far the most important medium for launching a national campaign, especially since the audience has not yet fragmented in the way that it has in the UK or US.
The main Brazilian terrestrial network, Globo, is still so dominant, in terms of both production values and audience share, that multi-channel subscriber TV has yet to make much of an impact.
"Pay-TV in Brazil is still tiny compared to other media, although it's showing huge growth," says Fernando Fernandes of the consultancy Booz Allen Hamilton.
"If you look at how many subscribers it has, they're still less than 10% of the total households in Brazil."
But whatever the medium, there is one aspect of Brazilian advertising that foreigners always find puzzling.
Estimates indicate that roughly half of the country's 183 million people are descended from African slaves, yet black people have traditionally been absent from most Brazilian adverts.
Sao Paulo's buildings could look a lot bleaker in future
There is a certain cruel economic logic to this. It has always been the case in Brazil that the lighter your skin colour, the more likely you are to belong to the higher socio-economic groups that advertisers want to reach.
But since economic reforms ended hyperinflation in the mid-1990s, Brazil's poorer citizens have acquired greater purchasing power, giving them more clout as consumers.
"Here in Brazil, we've always had a tendency to use stereotypes in advertising - Europeans who are very white with blue eyes and blond hair," says Vivian Bialski, who lectures in marketing and communications at Sao Paulo's advertising and marketing university, ESPM.
"This has been changing, fortunately. Ten years ago, it was as if Brazil was denying its own race, its own culture. Many Brazilian women are black, they're beautiful, they're gorgeous, so why don't we use that [in advertising]?"
As evidence of public concern about the issue, Ms Bialski quotes a 2002 survey by the Brazilian advertising association, ABP, in which 44% of respondents saw Brazilian advertising as discriminating against poor people and black people.
"It's not that it's changed tremendously since then, but it has begun to change and it will change more," she says.
"Black people used to appear in ads only when they were playing roles like the maid or the cleaning lady. Then it started to change. Now you can see them in ads for fashion, groceries, pharmaceutical products, even banks and universities.
More black Brazilians are becoming middle-class
"One reason is that black people started to migrate to the middle class and started to be a very important consumer market. They're not necessarily poor people any more - they have moved to a better economic position."
Not everyone agrees. Booz Allen Hamilton's Mr Fernandes argues that advertising is an aspirational medium and is not about depicting the social reality of Brazil's racial diversity.
"We see this diversity completely differently from Britain or the US," he said. "We don't need to express this in our advertising campaigns."
Many of DM9DDB's ads do in fact reflect Brazil's multi-racial society, with participants drawn from the country's different ethnic groups. But its chief executive, Sergio Valente, rejects the notion that advertising has a social obligation.
"Advertising exists to sell products. We don't have a social responsibility, we have a commercial responsibility," he says. "Social responsibility lies with human beings and human beings make advertising.
"It's my responsibility as an individual, but not my industry's. My industry's not made for that."
Back on the streets of Sao Paulo, Mr Kassab wants to replace the hoardings with "street furniture" - bus shelters, information panels and kiosks like the ones in London or Paris.
But while the format of Brazil's advertising may change, the debate about its content looks set to continue for some time to come.