From the above it would appear that the nomination technique offers few possibilities to determine the extent of cocaine use because of the lack of an adequate reference framework. Although in a survey the initial random selection of the sample is large it appears that this method is not suited to study the nature and size of cocaine use. Due to the low prevalence which may be expected a large (and thereby costly) sample is needed. Even in the case of a survey among a high-risk group, for example the age category of 20 to 40 years, the cost would be considerable. Furthermore we can not be sure of the reliability of the results due to the sensitive nature of the topic. A network analysis is not possible either since the questions asked relate only to characteristics. The best possibility of obtaining an estimate of the amount of cocaine use in Rotterdam is the snowball method, together with network analysis. In addition to this estimate of the extent of use, this approach also gives some insight into the spread and the dispersion of cocaine use. For this purpose the respondents have been questioned about other Rotterdam cocaine users they know.

For the description of the nature of cocaine use, so-called qualitative research methods will be used, based on the method and concepts of Janssen and Swierstra (1982). Drug use is considered not only as an individual activity, also socio-cultural and social aspects have to be taken into account. Extended interviews, looking at, for instance, drug careers, form the basis for the typology construction. Furthermore, several characteristics from these interviews are quantified. In addition a description of the opportunity structure will be presented on the basis of observations.

The method of data collection consists of a combination of snowball sampling and targeted sampling (Goodman 1961, Watters and Biernacki 1989). The principle of a snowball sample is that the initial respondents chosen at random are invited to give the names of others who meet the criterion drawn up by the researchers. In turn, the nominees are asked to give the names of others, etc. The inclusion criterion for both respondent and nominee in this study is that they have used cocaine a total of 25 times and/or five times in the last six months. It is however virtually impossible to choose cocaine users as initial respondents at random since we are dealing with a population which is difficult to track down. For this reason we decided to combine the technique of a snowball sample with the principle of targeted sampling.

In targeted sampling respondents of whom the researchers have good reason to believe they form a reasonable cross section of the research population are deliberately looked for. This is based on literature and preliminary study. In our study the targets in which respondents are looked for are settings of cocaine use. During the field work it may be shown that certain groups are present only in small numbers or missing altogether in the sample. It is also possible that the researchers discover a group which was previously unknown. If this happens an active search is made for respondents in these groups.

Eight settings were listed as possible areas of cocaine use based on an extensive literature study and interviews with key informants of police, drug assistance agencies, the courts, welfare services, youth work, and the cafe scene (Intraval 1990c). It is assumed that within these settings comparatively a large number of cocaine users can be found. These settings form the initial targets of the survey.

This is the setting about which we have most information. In Rotterdam, as in other cities, nearly all users of opiates are also taking cocaine, regularly or irregularly. An increasing number of addicts appear to indicate that cocaine is not only their main drug but has become their main problem.

Here we are looking at young people who gather in such places as youth clubs, community centres, coffee shops, and snackbars. Other groups are the so-called hooligans and homeless young people, who have often grown up in children's homes.

This refers to users from the circles of music, the theatre, art, the media etc.. It is generally supposed that cocaine is used in these circles, especially at parties.

This includes people working in advertising, fashion and other modern professions. This category is often mentioned in the same context as the above group. It is widely believed that a considerable amount of cocaine is used in these circles. Two sub-categories can be distinguished. On the one hand, there are the people who work very hard the whole week and take cocaine in the weekend, often in combination with (a lot of) alcohol. On the other hand, there are people with very demanding jobs and who take cocaine in order to keep going, also during the week.

This refers to people who regularly use cannabis or marihuana individually and in groups. It appears that there are scarcely any hashish circles left from which people take their identity, except perhaps in the case of the Surinamese Rastas.

This category refers in particular to juvenile delinquents, drug dealers and prostitutes (male and female). In street and sex club prostitution cocaine is used quite regularly in order, among other things, to be able to work longer hours.

This category includes students and staff at tertiary education institutes and universities. Cocaine is said to be often used during busy examination periods.

This refers to fitness centres and certain sports such as basketball, baseball, ice hockey and American football.

The eight settings served as the first guideline for the start of the field work. First a social map was made of the organisations, institutions, companies and associations that could be important to the study. This refers both to agencies which are specifically involved in (drugs) welfare as well as organisations which are targeted on specific (professional) groups. During the research this map became more detailed and was updated to include places, especially those outside the field of the (drug) assistance agencies, such as sport and fitness centres, sport clubs, galleries, practice rooms of musicians, artists' studios, and clubs (places where cocaine is said to be used). The various locations, institutions, organisations, companies and associations are ranked as far as possible according to the various settings. This made it possible to approach the field in a more targeted way and to establish contacts with various groups of users.

In our research a number of different approaches were used in order to come into contact with respondents. In this way it was possible to reach a group of cocaine users that was as heterogeneous as possible. Contact was made through:

In addition to conducting interviews, the field work included becoming acquainted with and observing the places where users gather (the so-called field). Through these activities the first contacts could be made with the cocaine users. Furthermore, additional information was obtained on the world of the users with special attention being paid to the following topics:

During the interviews which (on average) lasted more than two hours, use was made of a questionnaire made up of two parts, a qualitative part and a quantitative part. The qualitative part is an item list which is used as the basis for the interviews with the respondents. Relevant items are the background of the respondent; current lifestyle; first drug/alcohol experience; cocaine career; functions and effects of cocaine; current cocaine usage; income; criminal record; contact with (drugs) assistance agencies. In addition the respondent can refer to items which are important from his point of view. These discussions were recorded on tape. Subsequently they were processed and arranged with the help of the word processing programme WordPerfect. Furthermore, certain characteristics have been distilled from the in-depth interviews which are quantified and analyzed with SPSS (Statistical Package for the Social Sciences) and the text database programme AskSam.

The quantitative part was made up of questions with pre-coded answer categories. These concern the personal network of the respondent, namely the Rotterdam cocaine users known to him. The respondent began by making an estimate of the number of users known to him in the following five circuits in which cocaine is used: entertainment circuit (cafes, pubs, discotheques and so on), workplace, home circuit, hobby/sports, and hard drug scene. These five circuits were chosen so that respondents would not only name persons from their close environment but also users from more peripheral circles(4). In this way we were able to get a reasonable spread of contacts in which cocaine plays a role. The respondent was invited to name ten users (nominees) in each of the five circuits and to give information on: gender; age; first letters of first name and surname; any nickname; occupation; whether the contact takes place in connection with cocaine; and whether the nominee knows that the respondent takes cocaine. After that, two nominees were selected at random from each circuit with the help of a randomisation table. The respondent was asked questions about the nominee: length of the relationship with the nominee; whether he was present at nominee's first use of cocaine; current cocaine use of nominee; duration of cocaine use of nominee; most important place of use of cocaine of nominee; joint use; any link between respondent and nominee in procurement of cocaine. The answers of the quantitative part of the questionnaire were noted during the interview and subsequently processed with the database programme INGRES.

The two nominees with the lowest random figures were selected as follow-up respondents. If the respondent said that he could not, or did not want to, reach these nominees, he was asked which of the nominees he could contact. If the respondent said that he could not reach any nominee, he was requested to supply information on ways in which new nominees could be contacted.

Apart from the data collection through the interviews, information is obtained by way of observations in the field. Use was made of an observation scheme and field notes. These data have been processed and arranged with the word processing programme WordPerfect.

For a description of the nature of cocaine use in Rotterdam the qualitative part of the questionnaire is the most important. On the basis of the in-depth interviews types of cocaine users have been distinguished. The analysis technique applied was developed by the Criminology Institute of Groningen, in particular by the researchers Swierstra and Janssen (Janssen and Swierstra 1982, Janssen and Swierstra 1986). Later on this technique was applied and further developed by, among others, Intraval (1987, 1989 and 1991), Swierstra (1990) and De Bie and Miedema (1990). In this technique, the processed in-depth interviews form the basic material for analysis. First, the individual interviews were analyzed. Important, eye-catching and relevant elements were distilled from the individual stories. After that the distinctive differences and similarities were looked at. This was done on a categorical level since what we are interested in is not the individual, person-linked, differences but the differences and similarities between groups of users. At this stage the researchers looked at the conspicuous and, at times, extreme respondents who may serve as examples. Based on this, a first rough classification was made of categories of users. The first contours are then visible of the dimensions on which the types may be distinguished from each other. Next, with the help of the so-called minimum-maximum comparison method, the approximate classification was further refined. With this method, groups (types) are formed in such a way that differences within the groups are as small as possible and the differences between the groups as great as possible. Respondents placed under one type do not therefore have to score equally on all items but there must be similarities on the most characteristic relevant items (dimensions).

The quantitative part of the questionnaire is used for the description of the spread and dispersion of cocaine in Rotterdam and for the estimation of the number of users. In order to determine the extent of use, two estimators have been developed (Snijders 1991). These estimators have been derived from a combination of snowball random samples and the network approach(5). The estimators are based on a randomly selected initial sample. This was not the case for the initial sample in Rotterdam. In section 6.2 it is noted how these estimators are adapted to the selectness of the initial sample. A problem in estimating the extent of cocaine use was the ambiguous identification of persons in the network. We found that many respondents were unwilling to give the full name of cocaine users. For this reason we decided to identify people on the basis of a combination of personal characteristics. These characteristics are; first two letters of the first name and surname, nickname, gender, age and occupation. Furthermore, the quantitative part of the research is used, by means of analyzing personal networks, to investigate the structure of relationships (contacts) within the group of cocaine users. The nomination of different users in the five circuits forms the basis for the analysis of personal networks of the respondent. These networks are also analyzed with two-level regression analysis (multi-level analysis). The analysis is applied to relationships about which the respondent has given more specific information (6).

For clarity's sake, it must be mentioned that during the various research phases the qualitative and quantitative parts were more closely linked than might appear from what has been written above. In chapters five and six more attention will be paid to the minimum-maximum comparison method, the personal network analysis and the two-level regression analysis. They are developed and elaborated during the research and can be therefore seen as a kind of result.

In this section we describe the broad range of activities, carried out by the team of five field workers during the nine months of field work. It will be seen that the research results are based on intensive and detailed field work and that a good impression is gained of cocaine use and cocaine users in Rotterdam(7). The more than 120 locations and social events which were regularly frequented include cafes, galleries, the film ball, exhibitions, house parties, discotheques, coffee shops, youth clubs, sports meetings, fitness centres, football supporters' homes, informal meeting places for young people, gathering places for street prostitutes and sex clubs. In addition to the initial settings the team also studied and frequently visited other settings during the research. The aim of the field work is twofold, to get a good impression of the opportunity structure of cocaine use and to recruit respondents who form a good cross section of the (research) population.

The field work team began with a reconnaissance of the field. Together with people who are well acquainted with the Rotterdam situation, a first impression was obtained of the leisure scene and night life. At the same time contacts were established with cocaine users and a number of pilot interviews were held. The questionnaire was adjusted on the basis of the experience of these pilot interviews. After several months, the field work was intensified. Using an observation scheme there were kept notes of the observations and activities. A picture was obtained of the various leisure locations, the busiest times, the different (social) groups which frequent the locations, the movement of night life throughout the city, the open or secret use of cocaine, the use of other drugs, any dealer activities, etc. Where possible, contacts were established with users, and agreements made to participate in the survey. Also during these months, people with experience of cocaine use and who were willing to allow an interview were contacted through a number of organisations.

In the course of the field work, a large number of leisure settings and social events were visited. An important element of field work, in addition to observation, is going out in the evening, visiting the various pubs, cafes, discotheques etc., showing your face often and talking to people. The field workers tried in this way to gain the confidence of people and to discover to what extent they are acquainted with the use of cocaine in Rotterdam. The objective of the research was then explained in detail. If someone met the criteria an interview was arranged. Establishing contact directly with the users is a time-consuming method. It takes a lot of time to gain the confidence of people and convince them that it is important that they participate in the study. The impression gained was that the more the user was integrated in society, or had a higher social position, the more he or she has to lose. This means that it takes even more time to gain the confidence of such people and persuade them to participate. However, over time, intensive field work does pay dividends. The recruitment of respondents became increasingly smoother. The fact that more people became aware that a cocaine study was under way, and those participating considered it a mainly positive experience, began slowly but surely to bring results.

It has been known for some time that opiate users take drugs other than heroin and that cocaine has been playing a increasingly prominent role in this (Intraval 1989 and 1991, Grapendaal e.a. 1991). These poly-drug users form the most visible group of cocaine users and are the best known. Both the drug assistance agencies and the police have a lot of information on them. The evidence is that most of these people do in fact have experience of cocaine. It is rare that only heroin is taken. Both heroin and cocaine are used relatively openly. In addition to use at home, at the homes of friends or in dealers' premises, these drugs are also often taken outdoors, in toilets, doorways, or in telephone booths. The most well known assembly places in Rotterdam include the Central Station, the Nieuwe Binnenweg and the West-Kruiskade.

Drugs have for many years been popular in the world of art and culture. Examples of the stories of drug addict (jazz) musicians are well known. Artists are often seen as the vanguard or trendsetters, also in relation to the taking of (new) drugs. Two conflicting stories are circulating in Rotterdam concerning drug use in the art world. One story is that the users are found mainly among the younger artists. The other is that it is the older generation who are the drug takers. A gallery owner tells, however, that the last time he went in search of cocaine in the company of an artist was many years ago. No open consumption of cocaine was observed by the field workers who attended openings of exhibitions, inaugurations of galleries and similar events. Soft drugs were taken and alcohol was available in great quantities. This is not to say, however, that cocaine is not used by artists in Rotterdam. During the research activities people belonging both to the old guard and the group of younger artists were talked to and interviewed. There were no clear indications that the one group contains more drug users than the other. There was evidence, however, that the younger artists consider cocaine a pleasurable luxury while the older generation saw it more in the context of experimentation and a sign of being different. Cocaine is also used in the world of music. Musicians themselves and people with jobs related to music, such as roadies and sound technicians, admit that they occasionally take cocaine.

It is sometimes suggested that there is a relationship between hashish and the use of cocaine. This is reminiscent of the 'stepping stone' relationship which was established between hashish and heroin use. Few cocaine users were found among the people who go to coffee shops. The use of hashish is a widespread phenomenon which has been more or less accepted. Many people who were talked to during the fieldwork admitted taking or having taken hashish or marijuana some time or other. A direct link with cocaine use was not established. The talks and interviews with cocaine users do show, however, that many of them have experience of hashish, marijuana or weed.

As we have already said, the use of hashish is widespread. Young people form no exception. They are a significant part of the public which goes to coffee shops. Evidence from young people in youth centres, in informal meeting places and in pubs and cafes indicate that cocaine is another story. Despite the ban against the use of hard drugs in youth centres, these are taken in (or nearby) certain centres. Some youth centres have even acquired a reputation for drug use. Nevertheless, cocaine use does not appear to be really widespread among young people. If they take drugs they usually resort to speed and XTC. The lower price of speed certainly plays a role in this. Speed is seen as 'the poor man's coke'. The use among young people is more common in pubs and discos than in youth centres. The same applies to football supporters. There is no evidence of excessive use of cocaine by football supporters, as some people had suggested. Despite the yell 'hash, coke and pills that's what we want', the supporters take mostly alcohol and hashish before, and during, the matches they attend. If they take cocaine, it is mainly when visiting pubs/cafes.

During the field work, the arrest of the famous footballer Maradona in connection with cocaine taking, formed a major discussion point. The link between cocaine and sport has been shown more often. Cocaine use is said to be widespread, particularly in sports in which a relatively large number of Americans participate such as baseball, basketball, American football and ice hockey. There is no clear evidence of this from the observations of the field workers. Cocaine users were found in the most diverse sports, from athletics to kick boxing, but there is certainly no general use of cocaine among sports people. Cocaine is not a very appropriate means of doping and this probably plays a role. A number of users who have tried cocaine say the effect was either nothing or the reverse of what they wanted. They take it mostly in pubs and at parties and not to improve their sports performance. There was no evidence of excessive use of cocaine in fitness centres. In these circles, too, cocaine is used more in the context of leisure activities. The fitness centre may well play a role in this, of course, since for many people fitness training is a form of leisure activity. This is unrelated to people who are aiming at an improved sports performance and the like. The impression is, however, that if any drugs are taken in these circles they are more likely to be related to improved performance and are such drugs as anabolic steroids.

It is often suggested that cocaine is commonly used in the world of advertising, fashion and so on. People with busy, well-paid, jobs are said to be the main group of users. The evidence obtained in the field work points in another direction. The use of cocaine is no longer restricted to an elite group. Although cocaine use certainly does occur in these professions it is clearly evident that they do not (these days) form the main category. Cocaine use in this group is of a predominantly hidden nature. People are reluctant to talk about their cocaine use, at least towards third parties. They often say that if their use of cocaine were to be known to people other than their intimate friends, their position would be jeopardised. This probably explains why only a limited number of this category of users were prepared to cooperate with the study. It is also possible that the trend toward a more negative image of cocaine played a role in this.

The use of cocaine in direct relation to work does not occur very often. Some people told that this was counterproductive, certainly in the case of a responsible job. Within this group, too, cocaine use is mainly in the context of recreation. There is evidence that in the case of hard night work with long hours combined with a leisure atmosphere (pubs, taxis) there is some relationship to cocaine use.

The use of cocaine in order to get through an examination period appears to be one of the wild stories linked to the drug. None of the users who the field workers talked to or interviewed had ever used it in this context. Interviews with a number of (former) chairmen of students' associations revealed that incidents involving cocaine are very rare indeed. They do not have the impression that cocaine is in general use among students. Students themselves say that very few use any cocaine and if they use it they do not talk about it openly with others in their student group. Insofar as it is used, this is mainly at parties or in pubs.

In addition to the world of fast money, the semi-legal and, in particular, the illegal circuit, proved a difficult to reach group. Stories of respondents indicate that the relationship with cocaine in criminal surroundings is not limited to dealing. If cocaine is available it is usually also taken. The extent to which cocaine plays a role in criminal acts (in the way that alcohol is used, for example, to gain courage) is not clear at first sight. Within the semi-legal circuit of prostitution, cocaine plays a clear role. According to a number of dealers and prostitutes, cocaine is used in a number of sex clubs. Here, too, it is used in a more secretive way. Street prostitution is a more visible and accessible area. A large proportion of street prostitutes can be included in the poly-drug user category. In this sense, this group overlaps with the hard drug scene. Most of the group are addicted to opiates and work as a prostitute in order to finance their drug taking. In some cases their services are paid for in (portions of) heroin and/or cocaine. It is striking that a number of this group state that taking cocaine has also a functional component for them. They can maintain their stamina for standing along the roadside and doing their work only with the help of cocaine (this applies most certainly to those who are also using heroin).

As said earlier, approaches were also made through a number of organizations in order to get people to participate in the survey. This method was used only incidently because of the specific character of the respondents who were obtained in this way. This applied in particular to respondents who were obtained through drug assistance agencies. These were mainly poly-drug users and cocaine users who had themselves taken up contact with the these organizations because they were having problems caused by drug taking. The users interviewed in prison also form a specific and select category. In order to obtain as broad a picture as possible of the group of cocaine users, it was decided to use an approach through the media. The idea behind this was that we could then reach people who do not go out a lot, do not go to coffee shops, sports meetings, fitness centres and such like, and are not known to (drug) assistance agencies. Advertisements were placed in the national and regional newspapers and in the Rotterdam free door-to-door newspapers. People with experience of cocaine use were invited to participate in the survey. Figure 2.1 shows the way in which contact was made with the respondents.

At the end of the field work, based on the observations of the fieldwork team, information from the interviews and information about nominees, there was impression that certain groups were largely, or entirely, excluded from the respondents. For this reason, in the last phase of the field work the researchers specifically sought out prostitutes, members of ethnic minorities and young people, so that these groups, too, would be sufficiently represented.

The above method of gathering data, in combination with the questionnaire which was used, provided information on 1,161 persons, comprising 110 respondents and 1,051 nominees (see diagram 2.1). The gender, age and job is known of all these persons. With regard to 382 nominees information is available relating, among other things, to the length of use, place of use, and method of obtaining cocaine. Most is naturally known about the 110 respondents. They were extensively questioned about their use of cocaine.

1. For reasons of readability, the masculine form will usually be used in this book.

2. If the user population consists of a large number of small groups which have no knowledge of each other's existence, a larger initial sample will be needed than if a more interwoven pattern exists (where every user is a friend of a friend of a friend of every other user).

3. Circuit means here: a group of people in which many relationships exist, or, in network terms: a part of a network with a high density of contacts.

4. There is a danger that otherwise the respondents will only name those people with whom they have a close relationship or people they hardly know (for reasons of privacy).

5. The definition of the snowball sample for Rotterdam is: The sample is selected at random from the population of cocaine users in Rotterdam. This is the initial sample. The people included in the initial sample subsequently nominate people whom they know to use cocaine. The newly named persons form the 'first snowball wave'.

6. Within this relatively new approach, the differences between respondents which influence the cocaine contacts, are taken into account.

7. One of the field workers, for instance, has visited, together with the S-side supporters of Feijenoord (Rotterdam soccer club), several matches, pubs and supporters' meetings. In addition he participated in training and games of American football and baseball. Another field worker spent many hours talking with the clientele of coffee shops, youth centres, fitness centres. A third field worker frequently visited art galleries and attended a broad variety of cultural manifestations.