By Steve Kingstone
BBC News, Sao Paulo
As many as one-fifth of youths in the drug gangs of Rio de Janeiro, Brazil, are killed within two years, usually by police, a new study has indicated.
Critics say police shoot first and ask questions later in Rio's favelas
The report's authors followed 230 young people belonging to gangs in Rio de Janeiro's favelas, or shanty towns, for two years.
The majority were black or of mixed race and in their late teens.
During the two year survey period one in five of those taking part was killed, in most cases by police.
The study was compiled by Observatorio de Favelas, an independent research group operating in the city's poorest communities.
The report's authors spoke to young men performing a range of paid roles for drug gangs.
Some were dealers, others worked as look-outs.
A third group were known as "soldiers", protecting their territory from rivals.
One-third of those questioned said they had joined a gang to make money and nearly half said they spent their earnings on clothes.
There are frequent shoot-outs between police and drug gangs
Other reasons offered for turning to crime included the feeling of power and the rush of adrenalin it gave.
But as the report makes plain, the reality of this world does not live up to the apparent glamour.
Sixty percent of those questioned worked for more than 10 hours a day.
Half were on duty seven days a week and a majority had been involved in armed conflicts with rival gangs.
Most pointedly, during the period of the survey 45 young people, or a fifth of those taking part, were killed.
The authors say two-thirds were shot dead by the police.
Rio's favelas are frequently the scene of shoot-outs between officers and gang members.
The report stresses that the police were also victims of the violence.
State-wide, 33 officers were killed last year but nonetheless there is an on-going debate here about the use of lethal force by Brazil's police.
Human rights groups say the instinct of many officers is to shoot first and ask questions later.
They also accuse state authorities of not doing enough to investigate such killings.
Although this survey focused on Rio, the issue also resonates in other big Brazilian cities, notably Sao Paulo.