Table 3

Parameters and estimates of community-cocaine consumption for combined survey method by frequency of use categories in four surveys

Survey—population 15–30 years
Frequency of use categories (per half year)Never1–4 times5–10 times11–25 times25–50 times50+timesTotal/average (CI)
Mean number of usage days per half year†02.57.51838116.5
Probability of use on any given day (%)‡01.44.19.920.863.7
Proportion of users among total age-group population (%)§95.3 (94.8–95.7)3.00.90.40.20.2100
Frequency of use among users (%)¶6320945100
Average per-user consumption, mg (pure)/week††6431565852240154 (71–237)
Survey—population 31–64 years
Frequency of use categories (per year)Never1–4 timesMonthlyWeeklyDaily, almost dailyTotal/average (CI)
Mean number of usage-days per year‡‡02.51252182.5
Probability of use on any given day (%)‡00.73.314.850.0
Proportion of users among total age-group population (%)§98.3 (97.2–99.4)0.90.50.30.1100
Frequency of use among users (%)¶5030155100
Average per-user consumption, mg (pure)/week††4422702106160 (37–283)
Survey—prison population
Frequency of use categories (per half year prior to incarceration)Never1–3 times per month or lessWeeklyDaily, almost dailyTotal/average (CI)
Mean number of usage-days per year‡‡01252182.5
Probability of use on any given day (%)‡03.314.250.0
Proportion of users among total population 15–64 years (%)§99.9 (99.7–100)0.060.030.01100
Frequency of use among users (%)¶632313100
Average per-user consumption, mg (pure)/week††1389003510767 (487–1048)
Survey—injectors/marginalised users
Frequency of use categories (per year)NeverLess than once a monthMonthlyWeeklyDaily, almost dailyTotal/average (CI)
Mean number of usage-days per year)‡‡061252182.5
Probability of use on any given day (%)‡01.63.314.250.0
Proportion of users among total population 15–64 years (%)§99.9 (99.6–100)0.060.010.010.02100
Frequency of use among users (%)¶55121221100
Average per-user consumption, mg (pure)/week††21422702106491 (217–765)
  • Mean number of usage-days per unit time and the probability of use on a given day. Estimates of the proportion of users in the total survey population, frequency of use among users and average weekly consumption.

  • †Midpoint of frequency category reported in each survey, set to 116.5 for those using more than 50 times per half year.

  • ‡Defined as a usage-day or a single 24 h period in which cocaine is consumed. Number of usage days per user, divided by 182.6 for half-year periods and 365.25 for 1-year periods.

  • §Number of users in each category divided by population figures of relevant age group.

  • ¶Number of users in each category divided by the total number of users.

  • ††For each category the total consumption of pure cocaine equals number of users * mean number of usage days * mean dose size * mean number of doses per day * purity. Average per user consumption per week of pure cocaine equals this amount divided by the number of users and 26 for half-year period and 52 for 1-year period. Mean dose size and mean number of doses per day vary from 0.1g and 2.5 doses in categories of lowest frequency to 0.25g and eight doses in categories of highest frequency.

  • ‡‡Midpoint of frequency category, but assuming six usage-months per year.