High School and Youth Trends
Trends in Use
Since 1975, the MTF has annually studied the extent of drug abuse among high school 12th-graders. The survey was expanded in 1991 to include 8th- and 10th-graders. It is funded by NIDA and is conducted by the University of Michigan's Institute for Social Research. The goal of the survey is to collect data on 30-day, annual, and lifetime* drug use among students in these grade levels. This, the 29th annual study, was conducted during 2003. (1)
These are the key findings from the 2003 MTF:
- The percentages of 8th- and 10th-graders using any illicit drug continued to decline and are at their lowest levels since 1993 and 1995, respectively.
- MDMA (Ecstasy) use decreased in each grade, continuing the decline that began in 2002.
- Marijuana use decreased significantly among 8th-graders.
- Use of LSD, amphetamines, and tranquilizers was down among 10th- and 12th-graders; use of steroids, crack cocaine, and heroin was down among 10th-graders.
- Use of OxyContin and Vicodin(2) in the past year remained stable but at rates high enough to raise concern; Vicodin was the second most frequently reported drug among seniors, after marijuana.
- Lifetime cigarette smoking decreased in each grade, but 30-day smoking only declined significantly for 12th-graders, suggesting a slowing in the decline in 30-day use among 8th- and 10th-graders.
- Alcohol use remained stable across the board. Attitudes toward substance use, often seen as harbingers of change in rates of use, showed favorable changes for marijuana and MDMA.
- Perceived availability of several illicit drugs, alcohol, and cigarettes declined significantly for 10th-graders.
Perceived Risk of Harm, Disapproval, & Perceived Availability
In addition to studying drug use among 8th-, 10th-, and 12th-graders, MTF collects information on three attitudinal indicators related to drug use. These are perceived risk of harm in taking a drug, disapproval of others who take drugs, and perceived availability of drugs.
The following attitudinal changes are from 2002 to 2003:
- All three grades showed an increase in perceived risk for regular marijuana use for the first time in several years. There has also been a decline in the perceived availability of marijuana since 2001 in all three grades.
- The perceived risk associated with the use of ecstasy has risen sharply in all three grades over the past several years, and this trend continued in 2003. Additionally, personal disapproval of ecstasy use has risen steadily since 2001.
- The perceived risk of inhalant use has declined among 8th- and 10th-graders over the past 2 years.(3)
Use Trends Specific Drugs
Cigarettes & Smokeless Tobacco
Cigarette use declined in each grade and several categories of use between 2002 and 2003. This follows several years of gradual decreases in cigarette smoking that started after 1996 for 8th-graders, 1997 for 12th-graders, and 1999 for 10th-graders. Twelfth-graders showed a statistically significant drop in 30-day use; all three groups showed significant decreases in lifetime use.
- Lifetime use: 8th grade—from 31.4 percent in 2002 to 28.4 percent in 2003; 10th grade—47.7 percent to 43.0 percent; 12th grade—57.2 percent to 53.7 percent.
- 30-day use: 8th grade—10.7 percent in 2002 to 10.2 percent in 2003; 10th grade—17.7 percent to 16.7 percent; 12th grade—26.7 percent to 24.4 percent.
- Daily use in past 30 days: 8th grade—5.1 percent in 2002 to 4.5 percent in 2003; 10th grade—10.1 percent to 8.9 percent; 12th grade—16.9 percent to 15.8 percent.
- Annual use of bidis (small, flavored cigarettes from India) declined among 12th-graders from 5.9 percent in 2002 to 4.0 percent in 2003. Annual use of Kreteks (clove-flavored cigarettes from Indonesia) was reported by 8.4 percent of 12th-graders in 2002, dropping to 6.7 percent in 2003.
Lifetime use of smokeless tobacco by 10th-graders declined from 16.9 percent in 2002 to 14.6 percent in 2003.
MDMA (Ecstasy)
Rates of MDMA use decreased significantly across all three grades for both annual and 30-day use. Annual use among 8th-graders decreased from 2.9 percent in 2002 to 2.1 percent in 2003; 10th grade—4.9 percent to 3.0 percent; 12th grade—7.4 percent to 4.5 percent. Over the past 2 years, annual prevalence of MDMA use has fallen by more than half among both 10th- and 12th-graders. From peak levels reached in 2001 in all three grades, annual prevalence has fallen from 3.5 percent to 2.1 percent among 8th-graders, from 6.2 percent to 3.0 percent among 10th-graders, and from 9.2 percent to 4.5 percent among 12th-graders.
Marijuana
Overall, there has been nearly a one-third decline in annual marijuana use among 8th-graders, dropping from the 1996 peak level of 18.3 percent to 12.8 percent in 2003. For 8th-graders in 2003, the annual marijuana use rate—12.8 percent—is the lowest rate since the 1996 peak of 18.3 percent.
Cocaine and Crack
Cocaine (powder) use showed few changes across the board from 2002 to 2003. After rising between 2001 and 2002, crack use also declined significantly among 10th-graders in both annual and 30-day measures.
Alcohol
Between 2001 and 2002, significant reductions in alcohol use were reported among 8th- and 10th-graders in several categories. Thirty-day prevalence of alcohol use remained level in all three grades, after decreasing in all three grades the previous year. Self-reported drunkenness in the past 30 days showed no systematic changes in 2003, though it dropped in all three grades in 2002.
A special question to measure the prevalence of drinking flavored alcoholic beverages (sometimes called "alcopops" or "malternatives") was included in the 2003 survey. Their use is found to be widespread among underage drinkers, with 56 percent of 12th-graders reporting annual use.
Heroin & Other Opiates
The annual prevalence of heroin use in 2003 is below recent peak rates in all three grades surveyed—0.9 percent versus 1.6 percent in 1996 among 8th-graders; 0.7 percent versus 1.4 percent in 2000 among 10th-graders; and 0.8 percent versus 1.5 percent in 2000 among 12th-graders. However, little further improvement was observed this year.
In 2003, 10.5 percent of 12th-graders reported annual use of Vicodin and 4.5 percent said they had used OxyContin in that time period. Although these rates are not statistically different from those for 2002, these patterns are disturbing. Vicodin became the second-ranking illicit drug among seniors in 2003, after marijuana. These drugs are synthetic narcotics and carry a significant risk of addiction and other adverse effects.
Inhalants
After a long and substantial decline in the use of inhalants by 8th-graders, with annual prevalence falling from 12.8 percent in 1995 to 7.7 percent in 2002, a significant increase (to 8.7 percent) was observed in 2003 for this grade, but not among the upper grades. The perceived dangers of inhalant use have declined among both 8th- and 10th-graders over the past 2 years.
Hallucinogens
There was no significant change in 2003 at any grade level in the annual prevalence of use of any hallucinogen other than LSD. The use of LSD by adolescents has been declining since recent peak levels were attained in all three grades in 1996. Among 12th-graders, annual prevalence declined from 6.6 to 1.9 percent from 2001 to 2003; among 10th-graders, from 4.1 to 1.7 percent; and among 8th-graders, from 2.2 to 1.3 percent.
(1) For the 2003 MTF, more than 48,500 students in 392 schools nationwide were surveyed about lifetime, annual, 30-day, and daily
use of drugs, alcohol, and cigarettes and smokeless tobacco. The latest data are online at www.drugabuse.gov.
(2) For more information on the misuse or nonmedical use of pain medications or other prescription drugs, please visit www.drugabuse.gov and click on Prescription Medications under Drugs of Abuse.
(3) Questions on attitudes regarding inhalant use are not asked of 12th-graders.
Monitoring the Future Study: Trends in Prevalence of Various Drugs for 8th-Graders, 10th-Graders, and 12th-Graders*
2001-2003
|
8th-Graders |
10th-Graders |
12th-Graders |
|
2001 |
2002 |
2003 |
2001 |
2002 |
2003 |
2001 |
2002 |
2003 |
Any Illicit Drug Use |
lifetime
annual
30-day |
26.8
19.5
11.7 |
24.5
17.7
10.4
|
22.8
16.1
9.7
|
45.6
37.2
22.7 |
44.6
34.8
20.8
|
41.4
32.0
19.5
|
53.9
41.4
25.7 |
53.0
41.0
25.4
|
51.1
39.3
24.1
|
Marijuana /Hashish |
lifetime
annual
30-day
daily |
20.4
15.4
9.2
1.3 |
19.2
14.6
8.3
1.2
|
17.5
12.8
7.5
1.0
|
40.1
32.7
19.8
4.5 |
38.7
30.3
17.8
3.9
|
36.4
28.2
17.0
3.6
|
49.0
37.0
22.4
5.8 |
47.8
36.2
21.5
6.0
|
46.1
34.9
21.2
6.0
|
Inhalants |
lifetime
annual
30-day |
17.1
9.1
4.0 |
15.2
7.7
3.8
|
15.8
8.7
4.1
|
15.2
6.6
2.4 |
13.5
5.8
2.4
|
12.7
5.4
2.2
|
13.0
4.5
1.7 |
11.7
4.5
1.5
|
11.2
3.9
1.5
|
Hallucinogens** |
lifetime
annual
30-day |
5.2 3.4 1.6 |
4.1
2.6
1.2
|
4.0
2.6
1.2
|
8.9 6.2
2.1 |
7.8
4.7
1.6
|
6.9
4.1
1.5
|
14.7 9.1 3.3 |
12.0
6.6
2.3
|
10.6
5.9
1.8
|
LSD |
lifetime
annual
30-day |
3.4
2.2
1.0 |
2.5
1.5
0.7
|
2.1
1.3
0.6
|
6.3
4.1
1.5 |
5.0
2.6
0.7
|
3.5
1.7
0.6
|
10.9
6.6
2.3 |
8.4
3.5
0.7
|
5.9
1.9
0.6
|
Cocaine |
lifetime
annual
30-day |
4.3
2.5
1.2 |
3.6
2.3
1.1
|
3.6
2.2
0.9
|
5.7
3.6
1.3 |
6.1
4.0
1.6
|
5.1
3.3
1.3
|
8.2
4.8
2.1 |
7.8
5.0
2.3
|
7.7
4.8
2.1
|
Crack Cocaine |
lifetime
annual
30-day |
3.0
1.7
0.8 |
2.5
1.6
0.8
|
2.5
1.6
0.7
|
3.1
1.8
0.7 |
3.6
2.3
1.0
|
2.7
1.6
0.7
|
3.7
2.1
1.1 |
3.8
2.3
1.2
|
3.6
2.2
0.9
|
Heroin |
lifetime
annual
30-day |
1.7
1.0
0.6 |
1.6
0.9
0.5
|
1.6
0.9
0.4
|
1.7
0.9
0.3 |
1.8
1.1
0.5
|
1.5
0.7
0.3
|
1.8
0.9
0.4 |
1.7
1.0
0.5
|
1.5
0.8
0.4
|
Tranquilizers*** |
lifetime
annual
30-day |
5.0 2.8 1.2 |
4.3
2.6
1.2
|
4.4
2.7
1.4
|
9.2 7.3 2.9 |
8.8
6.3
2.9
|
7.8
5.3
2.4
|
10.3 6.9 2.9 |
11.4
7.7
3.3
|
10.2
6.7
2.8
|
Alcohol |
lifetime
annual
30-day
daily
|
50.5
41.9
21.5
0.9 |
47.0
38.7
19.6
0.7
|
45.6
37.2
19.7
0.8
|
70.1
63.5
39.0
1.9 |
66.9
60.0
35.4
1.8
|
66.0
59.3
35.4
1.5
|
79.7
73.3
49.8
3.6 |
78.4
71.5
48.6
3.5
|
76.6
70.1
47.5
3.2
|
Cigarettes (any use) |
lifetime
30-day
1/2 pack+/day |
36.6
12.2
2.3 |
31.4
10.7
2.1
|
28.4
10.2
1.8
|
52.8
21.3
5.5 |
47.4
17.7
4.4
|
43.0
16.7
4.1
|
61.0
29.5
10.3 |
57.2
26.7
9.1
|
53.7
24.4
8.4
|
Smokeless Tobacco |
lifetime
30-day
Daily |
11.7
4.0
1.2 |
11.2
3.3
0.8
|
11.3
4.1
0.8
|
19.5
6.9
2.2 |
16.9
6.1
1.7
|
14.6
5.3
1.8
|
19.7
7.8
2.8 |
18.3
6.5
2.0
|
17.0
6.7
2.2
|
Steroids |
lifetime
annual
30-day |
2.8
1.6
0.7 |
2.5
1.5
0.8
|
2.5
1.4
0.7
|
3.5
2.1
0.9 |
3.5
2.2
1.0
|
3.0
1.7
0.8
|
3.7
2.4
1.3 |
4.0
2.5
1.4
|
3.5
2.1
1.3
|
MDMA |
lifetime
annual
30-day |
5.2
3.5
1.8 |
4.3
2.9
1.4
|
3.2
2.1
0.7
|
8.0
6.2
2.6 |
6.6
4.9
1.8
|
5.4
3.0
1.1
|
11.7
9.2
2.8 |
10.5
7.4
2.4
|
8.3
4.5
1.3
|
Monitoring the Future Study: Trends in Prevalence of Various Drugs for 8th-Graders, 10th-Graders, and 12th-Graders**
1998-2000
|
8th-Graders |
10th-Graders |
12th-Graders |
|
1998 |
1999 |
2000 |
1998 |
1999 |
2000 |
1998 |
1999 |
2000 |
Any Illicit Drug Use |
lifetime
annual
30-day |
29.0
21.0
12.1 |
28.3
20.5
12.2 |
26.8
19.5
11.9
|
44.9
35.0
21.5 |
46.2
35.9
22.1 |
45.6
36.4
22.5
|
54.1
41.4
25.6 |
54.7
42.1
25.9 |
54.0
40.9
24.9
|
Marijuana /Hashish |
lifetime
annual
30-day
daily |
22.2
16.9
9.7
1.1 |
22.0
16.5
9.7
1.4 |
20.3
15.6
9.1
1.3
|
39.6
31.1
18.7
3.6 |
40.9
32.1
19.4
3.8 |
40.3
32.2
19.7
3.8
|
49.1
37.5
22.8
5.6 |
49.7
37.8
23.1
6.0 |
48.8
36.5
21.6
6.0
|
Inhalants |
lifetime
annual
30-day |
20.5
11.1
4.8 |
19.7
10.3
5.0 |
17.9
9.4
4.5
|
18.3
8.0
2.9 |
17.0
7.2
2.6 |
16.6
7.3
2.6
|
15.2
6.2
2.3 |
15.4
5.6
2.0 |
14.2
5.9
2.2
|
Hallucinogens |
lifetime
annual
30-day |
4.9
3.4
1.4 |
4.8
2.9
1.3 |
4.6
2.8
1.2
|
9.8
6.9
3.2 |
9.7
6.9
2.9 |
8.9
6.1
2.3
|
14.1
9.0
3.8 |
13.7
9.4
3.5 |
13.0
8.1
2.6
|
LSD |
lifetime
annual
30-day |
4.1
2.8
1.1 |
4.1
2.4
1.1 |
3.9
2.4
1.0
|
8.5
5.9
2.7 |
8.5
6.0
2.3 |
7.6
5.1
1.6
|
12.6
7.6
3.2 |
12.2
8.1
2.7 |
11.1
6.6
1.6
|
Cocaine |
lifetime
annual
30-day |
4.6
3.1
1.4 |
4.7
2.7
1.3 |
4.5
2.6
1.2
|
7.2
4.7
2.1 |
7.7
4.9
1.8 |
6.9
4.4
1.8
|
9.3
5.7
2.4 |
9.8
6.2
2.6 |
8.6
5.0
2.1
|
Crack Cocaine |
lifetime
annual
30-day |
3.2
2.1
0.9 |
3.1
1.8
0.8 |
3.1
1.8
0.8
|
3.9
2.5
1.1 |
4.0
2.4
0.8 |
3.7
2.2
0.9
|
4.4
2.5
1.0 |
4.6
2.7
1.1 |
3.9
2.2
1.0
|
Heroin |
lifetime
annual
30-day |
2.3
1.3
0.6 |
2.3
1.4
0.6 |
1.9
1.1
0.5
|
2.3
1.4
0.7 |
2.3
1.4
0.7 |
2.2
1.4
0.5
|
2.0
1.0
0.5 |
2.0
1.1
0.5 |
2.4
1.5
0.7
|
Tranquilizers |
lifetime
annual
30-day |
4.6
2.6
1.2 |
4.4
2.5
1.1 |
4.4
2.6
1.4
|
7.8
5.1
2.2 |
7.9
5.4
2.2 |
8.0
5.6
2.5
|
8.5
5.5
2.4 |
9.3
5.8
2.5 |
8.9
5.7
2.6
|
Alcohol |
lifetime
annual
30-day
daily
|
52.5
43.7
23.0
0.9 |
52.1
43.5
24.0
1.0 |
51.7
43.1
22.4
0.8
|
69.8
62.7
38.8
1.9 |
70.6
63.7
40.0
1.9 |
71.4
65.3
41.0
1.8
|
81.4
74.3
52.0
3.9 |
80.0
73.8
51.0
3.4 |
80.3
73.2
50.0
2.9
|
Cigarettes (any use) |
lifetime
30-day
1/2 pack+/day |
45.7
19.1
3.6 |
44.1
17.5
3.3 |
40.5
14.6
2.8
|
57.7
27.6
7.9 |
57.6
25.7
7.6 |
55.1
23.9
6.2
|
65.3
35.1
12.6 |
64.6
34.6
13.2 |
62.5
31.4
11.3
|
Smokeless Tobacco |
lifetime
30-day
Daily |
15.0
4.8
1.0 |
14.4
4.5
0.9 |
12.8
4.2
0.9
|
22.7
7.5
2.2 |
20.4
6.5
1.5 |
19.1
6.1
1.9
|
26.2
8.8
3.2 |
23.4
8.4
2.9 |
23.1
7.6
3.2
|
Steroids |
lifetime
annual
30-day |
2.3
1.2
0.5 |
2.7
1.7
0.7 |
3.0
1.7
0.8
|
2.0
1.2
0.6 |
2.7
1.7
0.9 |
3.5
2.2
1.0
|
2.7
1.7
1.1 |
2.9
1.8
0.9 |
2.5
1.7
0.8
|
MDMA |
lifetime
annual
30-day |
2.7
1.8
0.9 |
2.7
1.7
0.8 |
4.3
3.1
1.4
|
5.1
3.3
1.3 |
6.0
4.4
1.8 |
7.3
5.4
2.6
|
5.8
3.6
1.5 |
8.0
5.6
2.5 |
11.0
8.2
3.6
|
Monitoring the Future Study: Trends in Prevalence of Various Drugs for 8th-Graders, 10th-Graders, and 12th-Graders**
1995-1997
|
8th-Graders |
10th-Graders |
12th-Graders |
|
1995 |
1996 |
1997 |
1995 |
1996 |
1997 |
1995 |
1996 |
1997 |
Any Illicit Drug Use |
lifetime
annual
30-day |
28.5
21.4
12.4 |
31.2
23.6
14.6 |
29.4
22.1
12.9
|
40.9
33.3
20.2 |
45.4
37.5
23.2 |
47.3
38.5
23.0
|
48.4
39.0
23.8 |
50.8
40.2
24.6 |
54.3
42.4
26.2
|
Marijuana /Hashish |
lifetime
annual
30-day
daily |
19.9
15.8
9.1
0.8 |
23.1
18.3
11.3
1.5 |
22.6
17.7
10.2
1.1
|
34.1
28.7
17.2
2.8 |
39.8
33.6
20.4
3.5 |
42.3
34.8
20.5
3.7
|
41.7
34.7
21.2
4.6 |
44.9
35.8
21.9
4.9 |
49.6
38.5
23.7
5.8
|
Inhalants |
lifetime
annual
30-day |
21.6
12.8
6.1 |
21.2
12.2
5.8 |
21.0
11.8
5.6
|
19.0
9.6
3.5 |
19.3
9.5
3.3 |
18.3
8.7
3.0
|
17.4
8.0
3.2 |
16.6
7.6
2.5 |
16.1
6.7
2.5
|
Hallucinogens |
lifetime
annual
30-day |
5.2
3.6
1.7 |
5.9
4.1
1.9 |
5.4
3.7
1.8
|
9.3
7.2
3.3 |
10.5
7.8
2.8 |
10.5
7.6
3.3
|
12.7
9.3
4.4 |
14.0
10.1
3.5 |
15.1
9.8
3.9
|
LSD |
lifetime
annual
30-day |
4.4
3.2
1.4 |
5.1
3.5
1.5 |
4.7
3.2
1.5
|
8.4
6.5
3.0 |
9.4
6.9
2.4 |
9.5
6.7
2.8
|
11.7
8.4
4.0 |
12.6
8.8
2.5 |
13.6
8.4
3.1
|
Cocaine |
lifetime
annual
30-day |
4.2
2.6
1.2 |
4.5
3.0
1.3 |
4.4
2.8
1.1
|
5.0
3.5
1.7 |
6.5
4.2
1.7 |
7.1
4.7
2.0
|
6.0
4.0
1.8 |
7.1
4.9
2.0 |
8.7
5.5
2.3
|
Crack Cocaine |
lifetime
annual
30-day |
2.7
1.6
0.7 |
2.9
1.8
0.8 |
2.7
1.7
0.7
|
2.8
1.8
0.9 |
3.3
2.1
0.8 |
3.6
2.2
0.9
|
3.0
2.1
1.0 |
3.3
2.1
1.0 |
3.9
2.4
0.9
|
Heroin |
lifetime
annual
30-day |
2.3
1.4
0.6 |
2.4
1.6
0.7 |
2.1
1.3
0.6
|
1.7
1.1
0.6 |
2.1
1.2
0.5 |
2.1
1.4
0.6
|
1.6
1.1
0.6 |
1.8
1.0
0.5 |
2.1
1.2
0.5
|
Tranquilizers |
lifetime
annual
30-day |
4.5
2.7
1.2 |
5.3
3.3
1.5 |
4.8
2.9
1.2
|
6.0
4.0
1.7 |
7.1
4.6
1.7 |
7.3
4.9
2.2
|
7.1
4.4
1.8 |
7.2
4.6
2.0 |
7.8
4.7
1.8
|
Alcohol |
lifetime
annual
30-day
daily
|
54.5
45.3
24.6
0.7 |
55.3
46.5
26.2
1.0 |
53.8
45.5
24.5
0.8
|
70.5
63.5
38.8
1.7 |
71.8
65.0
40.4
1.6 |
72.0
65.2
40.1
1.7
|
80.7
73.7
51.3
3.5 |
79.2
72.5
50.8
3.7 |
81.7
74.8
52.7
3.9
|
Cigarettes (any use) |
lifetime
30-day
1/2 pack+/day |
46.4
19.1
3.4 |
49.2
21.0
4.3 |
47.3
19.4
3.5
|
57.6
27.9
8.3 |
61.2
30.4
9.4 |
60.2
29.8
8.6
|
64.2
33.5
12.4 |
63.5
34.0
13.0 |
65.4
36.5
14.3
|
Smokeless Tobacco |
lifetime
30-day
Daily |
20.0
7.1
1.2 |
20.4
7.1
1.5 |
16.8
5.5
1.0
|
27.6
9.7
2.7 |
27.4
8.6
2.2 |
26.3
8.9
2.2
|
30.9
12.2
3.6 |
29.8
9.8
3.3 |
25.3
9.7
4.4
|
Steroids |
lifetime
annual
30-day |
2.0
1.0
0.6 |
1.8
0.9
0.4 |
1.8
1.0
0.5
|
2.0
1.2
0.6 |
1.8
1.2
0.5 |
2.0
1.2
0.7
|
2.3
1.5
0.7 |
1.9
1.4
0.7 |
2.4
1.4
1.0
|
MDMA |
lifetime
annual
30-day |
-
-
- |
3.4
2.3
1.0 |
3.2
2.3
1.0
|
-
-
- |
5.6
4.6
1.8 |
5.7
3.9
1.3
|
-
-
- |
6.1
4.6
2.0 |
6.9
4.0
1.6
|
* "Lifetime" refers to use at least once during a respondent's lifetime. "Annual" refers to an individual's drug use at least once during the year preceding their response to the survey. "30-day" refers to an individual's drug use at least once during the month preceding their response to the survey.
** For hallucinogens, in 2001 "other psychedelics" was changed to "other hallucinogens" on the MTF survey forms, and mushrooms ("shrooms") was added. For 2001, half the students sampled received the original survey question and the other half the revised question. To trend the findings from 2000 to 2001, the researchers used the old item in the 2001 data; to trend from 2001 to 2002, they used the new item. In the table
above, the researchers show a break between 2000 and 2001, indicating a technical discontinuity.
*** For tranquilizers, in 2001 "Miltown" was removed and "Xanax" was added on the MTF survey forms. For 2001, half the students sampled received the original survey question and the other half the revised question. To trend the findings from 2000 to 2001, the researchers used the old item in the 2001 data; to trend from 2001 to 2002, they used the new item. In the table above, the researchers show a break between 2000
and 2001, indicating a technical discontinuity.
|