Commentary

In this section, a general review is provided of the data found in the accompanying tables of the statistical bulletin. In the future, this section will also include detailed analysis of the data tables and comment on the relationships between the data from different indicators. As this is the first issue of the bulletin, commentary will be limited to describing the extent of the historical data and the breadth of coverage across all the EU countries, and on how this impacts on the interpretation of the tables. Readers are reminded that they should refer to Methods and definitions for the technical detail necessary to make a sound interpretation of the data and for understanding the extent to which the data provided for different countries and for different years can be compared.

The majority of data found in the statistical tables is derived through national reporting registers and is structured by calendar year. For the most part, this corresponds to national reporting practice, although there are a few areas where this is not the case and Member States use a different time period, for example, on a six-monthly basis or financial year. Where this is the case, a methodological note alerts readers. As data collected at Member State level in one year will require time for collation, the information will only be available in the following year or sometimes even later. Similarly, the EMCDDA requires time to collate the national reports it receives and to prepare its annual report and the accompanying data tables. Thus, a two-year delay is unavoidable in the reporting cycle at European level for statistical data and so, in the 2004 annual report the most recent data provided in the tables will be for 2002.

Analysis of trends is complicated further by the fact that Member States do not necessarily collect all data on a regular, yearly basis. Whilst some data sets, such as drug-related deaths, treatment reporting or reporting on drug law offences or seizures, do lend themselves to being monitored in annual registries, other types of data do not. For example, the expense of conducting population and schools surveys or special estimates of the prevalence of problem drug use means that annual data are not always available. Thus, the most recently available data in these areas may not be for 2002 and, as a consequence, making comparisons between countries for data collected in the same year is not always possible. Encouragingly though, recent general population survey data are available for 20 countries, including five of the newer Member States.

It is also important to note that a time delay in processing all cases at Member State level may mean that it is necessary to revise data from the preceding year(s), so that in its 2002 reporting, a Member State may make some changes in data it provided for 2001. Data from the criminal justice system is particularly prone to such revision. However, usually the changes made are minor in nature and do not affect the overall interpretation of national figures.

Wherever possible, data are provided at national level. Historical data from Germany is separated for East and West Germany for the years prior to unification. Where national level data are not available, regional or city level data are supplied and, again, the reader is alerted. In a few tables, sub-regional data are also provided, where they are considered to provide additional useful information. This is particularly the case for the problem drug use and infectious diseases prevalence tables, where understanding the variation in sub-populations is especially useful and where national estimates are sometimes derived from such local studies by some form of synthesised or extrapolated estimate.

Sampling and coverage in the collection of the data are important issues in the interpretation of national data. For example, treatment report data are derived from systems that may only have partial coverage of the national treatment capacity or only cover particular sectors of the drug treatments available in Member States. For treatment demand data and first treatment demand data, double-counting of the same individual in registers is also an issue, although most systems attempt to control for this.

It is important to consider the historical context of the collection of harmonised data on drug use in Europe when viewing the statistical tables and, in particular, the time series data that are available. The EMCDDA has now been in existence for ten years and during this period it has worked with Member States to develop harmonised indicators with common reporting formats. This developmental process is reflected in the tables, which have become more comprehensive and more comparable in recent years.

In some areas, such as reporting on treatment demand, work was already in progress under the auspices of the epidemiological expert group of the Pompidou Group of the Council of Europe before the founding of the EMCDDA. Subsequent developments have benefited from this, both in terms of having available already developed methodological tools and in having a number of countries collecting data using broadly compatible methods. In some other areas, such as the recording of drug offences or drug seizures, many states have routinely collected this information, even if the level of comparability in reporting practice has been poor. This is evident in the data tables provided on drug seizures and drug law offences, where relatively long time series data are available and, in some areas at least, the number of Member States reporting is high. Nonetheless, data comparability problems are considerable and reporting practices vary substantially across countries.

In other indicator areas, such as problem drug use, drug-related deaths and, to some extent, the reporting of infections among drug injectors, a European data set hardly existed, even though reporting had been undertaken in some countries. The task here has been to work with the Member States to create a common set of definitions and to encourage investment in appropriate data collection activities. In these areas, the time series data are often quite limited, but considerable progress can be noted in the later reporting years, in general from 1998 onwards.

In summary, when considering the countries that were reporting prior to EU enlargement in 2004, namely, the “old” 15 EU Member States and Norway (who cooperates with the EMCDDA under special agreement), data are available going back in some tables to the early 1990s or before; however, the number of countries reporting in those early years is generally very small and data comparability is more compromised.

Overall data availability for the new Member States to the EU is more limited, with some notable exceptions. Although this year sees the first consolidated report from all 25 Member States and Norway, the EMCDDA has been working for several years (supported by the PHARE programme) to establish drug information systems. This is reflected in the fact that some of the new Member States have an impressive visibility in the data tables for the more recent years of reporting (2000 onwards) but still, as would be expected, historical data availability is far weaker. To make the tables easier to read, where no data are available for a country, the county is usually not shown; and for the same reason in a few tables, where data from the new Member States is limited and would make a very sparse table, they are shown grouped separately.

Where the data permit, the tables present prevalence rates. However, for many of the tables, the reporting units used or methodological considerations mean that it is more appropriate to present absolute numbers. The considerable heterogeneity of countries in population size and the differences in the nature of national drug situations are reflected in considerable heterogeneity in the scale of the national absolute figures. The reader should therefore be very cautious in drawing conclusions from overall European trends about the trend for an individual country, or vice versa, because European trends often are heavily influenced by the data from a few large countries. Similarly, the failure of a large country to report in for a particular year can markedly influence the overall European trend for that year and the overall pattern of the data.

The tables in the bulletin seek to present a unified picture for the EU Member States and also to highlight important differences. Due to the inherent difficulties in collecting data on illicit drug use, especially with respect to sampling issues, the reader is advised to use caution in drawing conclusions based on small differences. Assessing the significance of differences between countries and changes over time in a more technical fashion is usually impossible with the information currently reported to EMCDDA. In analysing the data from these tables it is therefore always important to consider the more general picture, to note the overall influence of each particular country and to bear in mind the differences in national trends from overall European trends.