1998 National Household Survey on Drug Abuse

Table 41. Estimated Number (in Thousands) of Persons Who First Used Marijuana During Each Year 1965-1997, Their Mean Age at First Use, and Annual Age-Specific Rates of First Use (per 1000 Person-Years of Exposure), Based  on 1994-1998 NHSDAs

			AGE-SPECIFIC RATE OF FIRST USE1
YEAR	INITIATES (1000s)	MEAN AGE	12-17	18-25	26-34
1965	601	18.9	8.7	13.7	4.1
1966	977	20.0	13.9	23.5	3.7
1967	1423	19.8	15.6	38.8	7.2
1968	1621	19.0	20.1	45.2	3.6
1969	2245	19.2	31.7	54.1	6.1
1970	2611	19.2	35.1	64.3	9.7
1971	2710	18.8	40.8	65.9	11.3
1972	2861	18.6	48.4	64.1	11.9
1973	2897	18.3	60.2	57.7	7.9
1974	2966	18.5	57.6	61.7	9.4
1975	3128	18.5	67.8	57.8	11.2
1976	2786	18.7	59.5	52.4	10.3
1977	2889	19.0	66.7	50.2	9.6
1978	2846	17.8	75.2	49.9	6.8
1979	2654	18.2	60.6	59.0	5.1
1980	2499	18.4	59.2	56.0	6.7
1981	2115	17.9	54.3	43.1	4.4
1982	1964	18.2	48.2	42.3	7.6
1983	2143	17.9	56.4	45.1	4.1
1984	2010	19.2	53.1	38.4	3.6
1985	1775	17.9	48.8	38.6	1.7
1986	1845	19.3	48.4	41.3	3.9
1987	1756	17.9	48.4	40.5	1.9
1988	1565	17.5	44.9	36.9	2.1
1989	1371	17.9	37.0	32.8	2.3
1990	1423	17.7	36.9	36.6	2.4
1991	1415	17.5	38.4	34.0	1.7
1992	1644	17.6	44.5	37.0	3.2
1993	1983	17.0	55.1	45.9	2.7
19942	2380	16.9	72.8	47.9	2.5
19953	2409	16.6	74.1	52.6	1.8
19964	2462	16.6	79.3	52.1	2.4
19975	2114	17.1	64.4	47.1	1.4

*Low precision; no estimate reported.

**Estimate rounds to zero.

¹ The numerator of each rate equals the number of persons who first used the drug in the year (times 1000). The denominator of each rate equals the number of persons who were exposed to risk of first use during the year, weighted by their estimated exposure time measured in years. For example, for the age group 12-17 in 1990, the denominator is the sum of three components:

(1) those persons 12-17 years old in 1990 who first used the drug in 1989 or earlier, times a weight of zero. The weight is zero since they had zero exposure to the risk of first use in 1990.

(2) those who first used the drug in 1990 times a weight of .5. The weight of .5 assumes that these people, on average, first used the drug at midyear and consequently have a half year of exposure (i.e. the first half of the year.)

(3) those who never used, or those who first used the drug in 1991 or later, times a weight of one. The weight of one assumes their exposure to the risk of first use during 1990 was for the whole year.

Each person is also weighted by his/her sample weight.

² Estimated using 1995, 1996, 1997 and 1998 data only.

³ Estimated using 1996, 1997 and 1998 data only.

⁴ Estimated using 1997 and 1998 data only.

⁵ Estimated using 1998 data only.

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1994-1998.

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