U.S. Department of Justice

Office of Justice Programs

Bureau of Justice Statistics

Special Report

JULY 2016 NCJ 249756

Co-Offending Among Adolescents 

in Violent Victimizations, 2004–13

Barbara A. Oudekerk, Ph.D., and Rachel E. Morgan, Ph.D., BJS Statisticians

For the 10-year period 2004–13, adolescents ages 12 to 

17 committed 50.0 nonfatal violent victimizations per 

1,000 adolescents (figure 1). In this report, adolescents 

are persons ages 12 to 17, young adults are persons ages 18 

to 29, and adults are persons age 30 or older. The rate of 

violent victimizations committed by adolescents—or the 

adolescent violent victimizing rate—was slightly higher 

than the violent victimizing rate for young adults (45.2 per 

1,000 young adults). (See Calculating rates using the National 

Crime Victimization Survey text box for more information.) 

The violent victimizing rate for adolescents was more than 

3.5 times higher than the rate for adults age 30 or older 

(13.7 victimizations per 1,000 adults).

More nonfatal violent victimizations were committed 

by adolescents who acted alone than adolescents who 

acted with co-offenders. Adolescents who acted alone 

committed 31.8 violent victimizations per 1,000 adolescents. 

In comparison, adolescents who acted with at least one 

co-offender committed 18.1 violent victimizations per 1,000 

adolescents. However, co-offending violent victimizing rates 

were higher for adolescents than for young adults (12.9 per 

1,000) or adults (1.9 per 1,000).

HIGHLIGHTS

This report uses data from the National Crime Victimization 

Survey (NCVS) to describe victim, incident, and offender 

characteristics of nonfatal violent victimizations committed by 

adolescents ages 12 to 17 acting alone or with co-offenders 

for the 10-year period 2004 through 2013. Violence includes 

simple assault and serious violent victimization (rape or sexual 

assault, robbery, and aggravated assault):

 Adolescent offenders who acted alone or with others 

committed 50.0 nonfatal violent victimizations per 

1,000 adolescents.

 Adolescent offenders committed 22% of all violent 

victimizations, while making up 10% of the U.S. population 

age 12 or older during this period.

 In violent victimizations committed by adolescents who 

acted with at least one other person, co-offenders were most 

commonly other adolescents (59%) or young adults (28%).

 More violent victimizations were committed by adolescents 

who acted alone (64%) than those who acted with 

co-offenders (36%).

 Simple assaults made up a greater percentage of violent 

victimizations committed by adolescents acting alone (77%) 

or with other adolescents (71%), compared to victimizations 

by adolescents acting with young adults (53%). 

 A greater percentage of adolescents who acted alone (61%) 

or with young adults (70%) used a weapon when engaging 

in serious violence than those who co-offended with other 

adolescents (50%).

 The rate of serious violent victimizations committed by 

adolescent offenders decreased 83% from 1994 to 2013. 

Figure 1

Violent victimizing rates, by offender age group and 

co-offending status, 2004–13

0

10

20

30

40

50

Oenders who acted 

with co-oenders

Oenders who acted alone

Total

Adolescents Young adults Adults

Rate per 1,000 adolescents

Note: Violent victimizations include rape or sexual assault, robbery, aggravated 

assault, and simple assault. Victimizing rates are calculated as the number of 

victimizations committed by a specific age group divided by the total population 

of that age group. Excludes victimizations in which the offender age group 

was unknown or all known offenders were age 11 or younger. For this report, 

adolescents are persons ages 12 to 17, young adults are persons ages 18 to 29, 

and adults are persons age 30 or older. See appendix table 1 for estimates and 

standard errors.

Source: Bureau of Justice Statistics, National Crime Victimization Survey, 2004–13.
CO-OFFENDING AMONG ADOLESCENTS IN VIOLENT VICTIMIZATIONS, 2004–13 | JULY 2016 2

This report uses data from the National Crime Victimization 

Survey (NCVS) to provide detailed information about 

nonfatal violent victimizations committed by adolescents 

acting alone or with co-offenders. The NCVS collects data 

on victims’ reports of their experiences. The majority of 

this report includes only victimizations in which victims 

reported the perceived age of their offenders and all 

known offenders were age 12 or older (87% of all violent 

victimizations from 2004 through 2013).

This report presents aggregate estimates for the period from 

2004 through 2013. Trend estimates are based on 2-year 

rolling averages centered on the most recent year from 1993 

to 2013. For example, estimates reported for 1994 represent 

the average estimates for 1993 and 1994. This report refers 

to all 2-year estimates by the most recent year. Rolling 

averages and aggregating years increases the reliability and 

stability of estimates and facilitates comparisons of detailed 

victimization characteristics.

Calculating rates using the National Crime Victimization Survey

The NCVS produces annual victimization, incident, and 

prevalence rates for the residential population of the United 

States based on a sample from that population. It has also 

been used to generate offending rates.* This report examines 

victimizing rates, or the rate at which specific groups commit 

victimizations (rather than offenses or incidents), focusing 

specifically on adolescent victimizing rates.

The following examples illustrate the difference between 

adolescent victimizing rates and adolescent offending, 

victimization, and incident rates. It shows how each rate 

would be calculated if three adolescent offenders robbed 

three victims—one adult and two adolescents—at gunpoint.

 Victimizing rates are calculated as the number of 

victimizations committed by a specific group divided by 

the total population of the group. The victimizing rate does 

not include the number of offenders who committed the 

victimizations. The incident above would contribute three 

victimizations to the adolescent victimizing rate because 

the adolescents victimized three different people.

 Offending rates are calculated as the number of offenders 

from a specific group who are involved in each incident, 

summed across all incidents, and divided by the total 

population of the group. Offenders may commit multiple 

crimes in a given year, and each offender would be counted 

separately in each incident. The incident above would 

contribute three offenders to the adolescent offending rate 

because three adolescents committed the incident.

 Victimization rates are calculated as the number of 

victimizations committed against a specific group divided 

by the total population of the group. If a crime incident has 

more than one victim, each victim is counted separately. 

The incident above would contribute two victimizations 

to the adolescent victimization rate because two of the 

victims were adolescents.

 Incident rates are calculated as the number of incidents 

(criminal acts) that occurred within a specific group divided 

by that population. An incident is counted only once 

regardless of the number of victims. The robbery above 

would contribute one incident to the adolescent incident 

rate because the two adolescents were robbed in the 

same incident.

Both victimizing and offending rates are based on information 

about offenders of crime. This report presents victimizing rates 

because it includes the number and nature of victimizations 

committed by adolescents, and permits estimates of the 

amount of victim harm generated by adolescent offenders 

who acted alone compared to those who acted with others. 

Offending rates would not accurately achieve these goals. 

Offending rates would produce duplicate counts of harm 

rendered to one victim if the incident was committed by 

more than one adolescent offender. For example, three 

adolescents committing serious violence against one victim 

would be described as “three adolescents committed a serious 

violent crime” based on the offending rate, but as “one victim 

seriously victimized by adolescents” based on the victimizing 

rate. The greater the number of adolescents who committed 

victimizations with co-offenders and the greater the number 

of co-offenders per victimization, the greater the count of 

victim harm. Therefore, offending rates could produce inflated 

estimates of victim harm.

Offending rates could also underestimate the amount of 

victim harm caused by adolescents. Offending rates count 

the number of offenders per incident and not the number of 

victims. For example, one adolescent who committed serious 

violence against three victims would be described as “one 

adolescent committed a serious violent crime” based on the 

offending rate but “three persons seriously victimized by an 

adolescent” based on the victimizing rate.

*Lynch, J. P. & Snyder, H. N. (2012). Juvenile crime trends and their 

implications for understanding. Understanding the “Whys” Behind 

Juvenile Crime Trends, 17-49. Available at http://whysproject.org/

whysFull.pdf.
CO-OFFENDING AMONG ADOLESCENTS IN VIOLENT VICTIMIZATIONS, 2004–13 | JULY 2016 3

Adolescents committed 22% of violent victimizations 

but made up 10% of the U.S. population

During 2004–13, adolescents were offenders in 22% 

of total violent victimizations known to be committed 

by persons ages 12 and older (table 1). In comparison, 

adolescents made up 10% of the U.S. population age 12 or 

older during this time. Violent victimizations committed 

by adolescents involved co-offenders 36% of the time 

(table 2). Co-offenders were most often other adolescents 

(59%). Another 28% of violent victimizations committed by 

co-offending adolescents involved young adult co-offenders. 

Victimizations by co-offending adolescents were less 

likely to involve co-offending adults (7%) or co-offending 

children age 11 or younger (4%). Of the average annual 

5,647,900 violent victimizations in which victims reported 

offenders’ age, adolescents who acted alone accounted for 

14% of victimizations, adolescents who co-offended with 

other adolescents accounted for 5% of victimizations, and 

adolescents who co-offended with young adults accounted 

for 2% of victimizations (table 3).

Table 1

Percent of total violent victimizations, by offender age group, 2004–13

Offender age group

Average annual 

victimizations Percent of total

Percent committed 

by persons ages 

12 or oldera Average annual U.S. population

Percent of 

U.S. population 

age 12 or older

Violent victimizations committed 

by persons ages 12 or oldera 5,647,900 87.3% 100% 253,004,700 100%

Any adolescent 1,251,100 19.3 22.2 25,003,000 9.9

Any young adult 2,274,100 35.1 40.3 50,306,400 19.9

Any adult 2,433,300 37.6 43.1 177,695,400 70.2

All children under age 12 77,265 1.2 ~ ~ ~

Unknown ages 744,683 11.5 ~ ~ ~

Total violent victimizations 6,469,870 100 ~ ~ ~

Note: Detail does not sum to total because victimizations can be committed by offenders in more than one age group. Violent victimizations include rape or sexual 

assault, robbery, aggravated assault, and simple assault. For this report, adolescents are persons ages 12 to 17, young adults are persons ages 18 to 29, and adults are 

persons age 30 or older. See appendix table 2 for standard errors.

~Not applicable.

aExcludes victimizations against persons age 12 or older in which the age of offender was unknown or all known offenders were age 11 or younger. 

Source: Bureau of Justice Statistics, National Crime Victimization Survey, 2004–13.

Table 2

Percent of violent victimizations committed by adolescents, 

by co-offending status, 2004–13

Adolescent co-offending status Percent

All violent victimizations 100%

Acted alone 63.5

Acted with co-offenders 36.1

All violent victimizations involving co-offenders 100%

All co-offenders age 17 or youngera 63.1

At least one age 11 or younger 3.7

All ages 12–17 59.3

Oldest co-offender age 18 or oldera 34.5

Ages 18–29 27.9

Age 30 or older 6.6

Average annual violent victimizations 1,251,100

Note: Detail may not sum to total due to rounding and missing data. Violent 

victimizations include rape or sexual assault, robbery, aggravated assault, 

and simple assault. For this report, adolescents are persons ages 12 to 17. See 

appendix table 3 for standard errors. 

aIncludes only those who co-offended.

Source: Bureau of Justice Statistics, National Crime Victimization Survey, 2004–13.

Table 3

Percent of violent victimizations, by offender age group and 

co-offending status, 2004–13

Offender age group and 

co-offending status

Average annual 

victimizations

Percent 

of total

Violent victimizations committed 

by persons ages 12 or oldera 5,647,900 100%

Adolescents who—

Acted alone 794,000 14.1%

Acted only with adolescents 268,100 4.7

Acted with young adults 126,100 2.2

Young adults who—

Acted alone 1,617,700 28.6%

Acted with young adults or adults 491,000 8.7

Adults who—

Acted alone 2,091,700 37.0%

Acted with adults 133,200 2.4

Otherb 126,200 2.2%

Note: Detail may not sum to total due to rounding and missing data. Violent 

victimizations include rape or sexual assault, robbery, aggravated assault, and 

simple assault. For this report, adolescents are persons ages 12 to 17, young 

adults are persons ages 18 to 29, and adults are persons age 30 or older. See 

appendix table 4 for standard errors.

aExcludes victimizations against persons age 12 or older in which the age of 

offender was unknown or all known offenders were age 11 or younger. 

bIncludes victimizations committed by persons age 11 or younger co-offending 

with anyone age 12 or older, adolescents co-offending with adults, and 

victimizations for which only the age of one offender was known. 

Source: Bureau of Justice Statistics, National Crime Victimization Survey, 2004–13.
CO-OFFENDING AMONG ADOLESCENTS IN VIOLENT VICTIMIZATIONS, 2004–13 | JULY 2016 4

Measuring offender age in the National Crime Victimization Survey

The NCVS collects information on nonfatal crimes reported 

and not reported to the police against persons age 12 

or older from a nationally representative sample of U.S. 

households. It asks respondents who report a victimization 

to indicate whether the crime was committed by a single or 

multiple offenders.

When an offender acted alone, the survey asks respondents 

to indicate whether they perceive the offender was age 11 

or younger; ages 12 to 14, 15 to 17, 18 to 20, or 21 to 29; or 

age 30 or older. When multiple offenders committed the 

crime, it asks respondents to provide perceived ages of the 

oldest and youngest offenders using the same age categories. 

Victimizations in which the victim could not estimate the 

age of the offenders and victimizations that were committed 

solely by offenders age 11 or younger were not included in 

this report. (See Methodology for more detail about offenders 

age 11 or younger and the limitations inherent in measuring 

offender age based on victim reports.)

In this report, offenders were grouped into three age groups: 

adolescents ages 12 to 17, young adults ages 18 to 29, and 

adults ages 30 or older. These larger age categories make 

it possible to reliably examine co-offending subgroups. In 

violent victimizations committed by two or more offenders in 

2004–13, co-offenders tended to be close in age. For violent 

victimizations in which the youngest offender was between 

ages 12 to 14, the oldest co-offenders were also ages 12 to 14 

in about 46% of the victimizations (table 4). In another 39% 

of these victimizations, the oldest co-offenders were ages 15 

to 17. Similarly, for violent victimizations in which the age of 

the youngest offender was 15 to 17, the oldest co-offender 

was most often ages 15 to 17 (42%) or ages 18 to 20 (35%). 

The majority (89%) of the youngest co-offenders who 

committed violent victimizations with young adults were ages 

15 to 17 (table 5).

Table 4

Percent of co-offenders involved in violent victimizations, by age of oldest and youngest offenders, 2004–13

Age of youngest offender

Age of oldest offender 12–14 15–17 18–20 21–29 30 or older

12–14 46.2% ~ ~ ~ ~

15–17 38.7 42.4% ~ ~ ~

18–20 5.0 34.7 31.4% ~ ~

21–29 2.1 12.8 42.2 60.2% ~

30 or older 7.2 6.5 23.4 37.2 100%

Average annual violent victimizations 197,900 236,000 238,400 266,900 133,200

Note: Detail may not sum to total due to rounding and because totals include victimizations for which the victim reported only the age of the youngest or oldest 

offender. Violent victimizations include rape or sexual assault, robbery, aggravated assault, and simple assault. See appendix table 5 for standard errors. 

~Not applicable.

Source: Bureau of Justice Statistics, National Crime Victimization Survey, 2004–13.

Table 5

Percent of adolescents who co-offended with young 

adults, by age of youngest and oldest offenders, 2004–13

Age of oldest offender

Age of youngest offender 18–29 18–20 21–29

12–14 11.1% 10.7% 12.2%

15–17 88.9 89.3 87.8

Average annual

violent victimizations 126,100 91,700 34,400

Note: Violent victimizations include rape or sexual assault, robbery, 

aggravated assault, and simple assault. For this report, adolescents are 

persons ages 12 to 17 and young adults are persons ages 18 to 29. See 

appendix table 6 for standard errors.

Source: Bureau of Justice Statistics, National Crime Victimization Survey, 

2004–13.
CO-OFFENDING AMONG ADOLESCENTS IN VIOLENT VICTIMIZATIONS, 2004–13 | JULY 2016 5

Co-offending adolescents were generally the same 

race and sex

During 2004–13, adolescents who acted alone to commit 

violent victimizations were most often male (72%). When 

violent victimizations were committed by co-offending 

adolescents, co-offenders were usually the same sex. 

Adolescent males were offenders in 62% of violent 

victimizations committed by adolescents who acted 

with other adolescents (table 6). About 64% of violent 

victimizations committed by adolescents who acted with 

young adults involved at least one male adolescent offender 

who acted with all males.

Violent victimizations committed by a group of adolescents 

involved a greater percentage of female offenders (26%) 

than those committed by adolescents who co-offended with 

young adults (10%). About a quarter (26%) of victimizations 

committed by adolescents who co-offended with young 

adults involved both male and female offenders.

More than half (59%) of violent victimizations committed 

by adolescents who acted alone were committed by white 

adolescents, and a quarter (26%) were committed by black 

adolescents. Co-offenders were all white or all black in 

three-quarters (75%) of violent victimizations committed 

by a group of adolescents and in over two-thirds (70%) of 

victimizations committed by adolescents who co-offended 

with young adults. From 2004 to 2013, the majority (66%) 

of victimizations committed by adolescents who acted with 

other adolescents involved two or three offenders (table 7). 

More than half of violent victimizations committed by 

adolescents who acted with young adults involved four or 

more offenders (56%), compared to 28% of victimizations 

committed by a group of adolescents. When victimizations 

were committed by adolescents co-offending with 

adolescents or young adults, almost half (42% to 50%) 

of victims did not know whether the adolescents were 

gang members.

Table 6

Percent of violent victimizations committed by adolescents, 

by offender demographic characteristics and co-offending 

status, 2004–13

Offender characteristic

Acted 

alone*

Acted with 

adolescents

Acted with 

young adults

Sex

Male 72.1% 62.4% † 63.9% ‡

Female 27.8 26.0 10.0 †

Male and female ~ 10.9 25.5

Race

White 59.0% 46.6% † 30.6% †

Black/African American 25.6 27.9 38.9 †

Other racea 10.8 3.1 † 8.7

Multiple offenders of various racesb ~ 13.2 18.7

Don’t know 4.6 6.1 0.8 †

Average annual 

violent victimizations 794,000 268,100 † 126,100 †

Note: Detail may not sum to total due to rounding and missing data. Violent 

victimizations include rape or sexual assault, robbery, aggravated assault, and 

simple assault. For this report, adolescents are persons ages 12 to 17 and young 

adults are persons ages 18 to 29. See appendix table 7 for standard errors.

*Comparison group.

†Significant difference from comparison group at the 95% confidence interval.

‡Significant difference from comparison group at the 90% confidence interval.

~Not applicable.

aPrior to 2012, offender race categories included white, black or African 

American, and other race. For 2012 and 2013, offender race categories were 

expanded to include American Indian or Alaska Native; or Asian, Native Hawaiian, 

or Other Pacific Islander; and single offenders of two or more races. Respondents 

were also asked if the offender was of Hispanic or Latino origin, however this 

category was excluded from the analysis because it cannot be determined if 

offenders were of Hispanic or Latino origin prior to 2012. See Methodology.

bIncludes multiple offenders who are of different races. Prior to 2012, this 

included white, black or African American, and other race. For 2012 and 2013, this 

included white; black or African American; American Indian or Alaska Native; or 

Asian, Native Hawaiian, or Other Pacific Islander. See Methodology.

Source: Bureau of Justice Statistics, National Crime Victimization Survey, 2004–13.

Table 7

Percent of violent victimizations committed by adolescents 

who co-offended, by number of co-offenders and gang 

status, 2004–13

Offender characteristic

Acted with 

adolescents*

Acted with 

young adults

Number of offenders

Two 42.4% 16.2% †

Three 23.9 23.0

Four or more 27.5 56.0 †

Gang status

Yes 18.9% 26.9% ‡

No 39.2 23.2 †

Don’t know 41.9 49.9

Average annual 

violent victimizations 268,100 126,100 †

Note: Detail may not sum to total due to rounding and missing data. Violent 

victimizations include rape or sexual assault, robbery, aggravated assault, and 

simple assault. For this report, adolescents are persons ages 12 to 17 and young 

adults are persons ages 18 to 29. See appendix table 8 for standard errors. 

*Comparison group.

†Significant difference from comparison group at the 95% confidence interval. 

‡Significant difference from comparison group at the 90% confidence interval.

Source: Bureau of Justice Statistics, National Crime Victimization Survey, 2004–13.
CO-OFFENDING AMONG ADOLESCENTS IN VIOLENT VICTIMIZATIONS, 2004–13 | JULY 2016 6

Simple assaults made up the majority of violent 

victimizations committed by adolescents

Violent victimizations committed by adolescents were 

more likely to be simple assaults than serious violent 

crimes (rape or sexual assault, robbery, or aggravated 

assault) if adolescents acted alone (77% for simple 

assaults compared to 23% for serious violent crimes) or 

co-offended with other adolescents (71% compared to 

29%) (table 8). In comparison, almost half (47%) of violent 

victimizations committed by adolescents who co-offended 

with young adults were serious crimes. Most serious 

violent victimizations committed by adolescents who acted 

alone (14%) or with young adults (27%) were aggravated 

assaults. In comparison, most serious violent victimizations 

committed by adolescents who co-offended with other 

adolescents were robberies (17%).

Most serious violence committed by adolescents did 

not result in injury

During 2004–13, a weapon was involved in a greater 

percentage of serious violent victimizations committed by 

adolescents who acted alone (61%) than serious violent 

victimizations committed by adolescents who co-offended 

with adolescents (50%) (table 9). About two-thirds (70%) of 

serious violent victimizations committed by adolescents who 

co-offended with young adults involved a weapon.

Although more than half of serious violent victimizations 

involved a weapon across these co-offending subgroups, the 

majority of adolescent-perpetrated violent victimizations did 

not involve weapons (73%), as most adolescent-perpetrated 

violence was simple assault. Among all violent victimizations 

committed by adolescents, which included serious violence 

and simple assault, fewer than 1 in 5 (17%) victimizations 

involved a weapon (not shown). 

Most serious violent victimizations committed by 

adolescents did not result in injury (59% to 70% across 

subgroups) (table 10). An injury was involved in a 

greater percentage of serious victimizations committed 

by adolescents who co-offended with young adults (41%) 

than with other adolescents (30%). An injury was involved 

in a slightly greater percentage of serious victimizations 

committed by adolescents who co-offended with young 

adults (41%) than by those who acted alone (32%). 

Table 8

Percent of violent victimizations committed by adolescents, 

by type of crime and co-offending status, 2004–13

Type of crime

Acted 

alone*

Acted with 

adolescents

Acted with 

young adults 

Serious violent victimizationsa 23.1% 29.1% † 46.9% †

Robbery 6.6 16.7 † 18.5 †

Aggravated assault 13.9 9.2 † 26.8 †

Simple assault victimizations 76.9% 70.9% ‡ 53.1% †

Average annual serious violent 

victimizationsa 183,600 78,100 † 59,200 †

Average annual simple 

assault victimizations 610,400 190,100 † 66,900 †

Note: For this report, adolescents are persons ages 12 to 17 and young adults are 

persons ages 18 to 29. See appendix table 9 for standard errors. 

*Comparison group.

†Significant difference from comparison group at the 95% confidence interval. 

‡Significant difference from comparison group at the 90% confidence interval.

aIncludes rape or sexual assault, robbery, and aggravated assault. 

Source: Bureau of Justice Statistics, National Crime Victimization Survey, 2004–13.

Table 9

Percent of serious violent victimizations committed by 

adolescents involving a weapon, by co-offending status, 

2004–13

Weapon use

Acted 

alone*

Acted with 

adolescents 

Acted with 

young adults 

Yes 61.3% 50.1% † 70.5% ‡

No 34.7 41.0 24.8 †

Don’t know 4.0 8.9 † 4.7 !

Average annual serious violent 

victimizations involving a weapon 112,600 39,100 † 41,700 †

Average annual serious 

violent victimizations 183,600 78,100 † 59,200 †

Note: Detail may not sum to total due to rounding and missing data. Serious 

violent victimizations include rape or sexual assault, robbery, and aggravated 

assault. For this report, adolescents are persons ages 12 to 17 and young adults 

are persons ages 18 to 29. See appendix table 10 for standard errors. 

*Comparison group.

†Significant difference from comparison group at the 95% confidence interval. 

‡Significant difference from comparison group at the 90% confidence interval.

! Interpret with caution. Estimate based on 10 or fewer sample cases, or 

coefficient of variation is greater than 50%.

Source: Bureau of Justice Statistics, National Crime Victimization Survey, 2004–13.

Table 10

Percent of serious violent victimizations committed by 

adolescents involving injury, by injury type and co-offending 

status, 2004–13

Victim injury

Acted 

alone*

Acted with 

adolescents

Acted with 

young adults

Yes 32.2% 30.4% 41.0% ‡

Serious injuriesa 14.9 4.7 ! † 16.9

Bruises, cuts, or other minor injuries 17.3 25.7 † 24.1 ‡

No 67.2% 69.6% 59.0% ‡

Average annual serious violent

victimizations involving an injury 59,200 23,700 † 24,300 †

Average annual serious 

violent victimizations 183,600 78,100 † 59,200 †

Note: Detail may not sum to total due to rounding and missing data. Serious 

violent victimizations include rape or sexual assault, robbery, and aggravated 

assault. For this report, adolescents are persons ages 12 to 17 and young adults 

are persons ages 18 to 29. See appendix table 11 for standard errors. 

*Comparison group.

†Significant difference from comparison group at the 95% confidence interval. 

‡Significant difference from comparison group at the 90% confidence interval.

! Interpret with caution. Estimate is based on 10 or fewer sample cases, or 

coefficient of variation is greater than 50%.

aIncludes sexual violence injuries, gunshot wounds, knife wounds, internal 

injuries, unconsciousness, and broken bones.

Source: Bureau of Justice Statistics, National Crime Victimization Survey, 2004–13.
CO-OFFENDING AMONG ADOLESCENTS IN VIOLENT VICTIMIZATIONS, 2004–13 | JULY 2016 7

This difference was due to a higher percentage of minor 

injuries in serious violence committed by adolescents 

who acted with young adults (24%) than alone (17%). 

The percentages of serious injuries were not significantly 

different for these two co-offending groups. Most injuries 

caused by adolescents who co-offended with other 

adolescents were bruises, cuts, or other minor injuries (26% 

of serious victimizations). Overall, including simple assaults 

and serious violence, 24% of total violent victimizations 

committed by adolescents resulted in an injury (not shown). 

Of these, 21% involved minor injuries and 3% involved 

serious injuries (not shown).

Police were notified in 71% of serious violent 

victimizations committed by adolescents who acted 

with young adults

More than two-thirds (71%) of serious violent victimizations 

committed by adolescents who co-offended with young 

adults were reported to police during 2004–13 (table 11). 

This was higher than in serious violent victimizations 

committed by adolescents who co-offended with other 

adolescents (51%) or acted alone (46%).

Across all offender ages and co-offending subgroups, 

smaller percentages of simple assault than serious violent 

victimizations were reported to police. Similar to the 

pattern of reporting serious violence to police, a greater 

percentage of simple assaults committed by adolescents 

who co-offended with young adults were reported to 

police (46%) than adolescents who co-offended with other 

adolescents (34%) or acted alone (25%). In addition, more 

simple assaults committed by adolescents who co-offended 

with other adolescents were reported to police, than those 

committed by adolescents who acted alone.

Table 11

Percent of violent victimizations committed by adolescents that were reported to police, by type of crime and co-offending 

status, 2004–13

Acted alone* Acted with adolescents Acted with young adults

Serious violent victimizations reported to policea

Yes 46.5% 50.6% 70.8% †

No 53.3 48.4 27.6 †

Average annual serious violent victimizations reported to policea 85,300 39,500 † 41,900 †

Average annual serious violent victimizationsa 183,600 78,100 † 59,200 †

Simple assault victimizations reported to police

Yes 24.7% 33.6% † 45.7% †

No 73.4 65.3 † 52.5 †

Average annual simple assault victimizations reported to police 150,900 63,900 † 30,600 †

Average annual simple assault victimizations 610,400 190,100 † 66,900 †

Note: Detail may not sum to total due to rounding and missing data. For this report, adolescents are persons ages 12 to 17 and young adults are persons ages 18 to 29. 

See appendix table 12 for standard errors. 

*Comparison group.

†Significant difference from comparison group at the 95% confidence interval.

‡Significant difference from comparison group at the 90% confidence interval.

aIncludes rape or sexual assault, robbery, and aggravated assault. 

Source: Bureau of Justice Statistics, National Crime Victimization Survey, 2004–13.
CO-OFFENDING AMONG ADOLESCENTS IN VIOLENT VICTIMIZATIONS, 2004–13 | JULY 2016 8

A greater percentage of victims were strangers 

in serious violence committed by co-offending 

adolescents than by adolescents who acted alone

During 2004–13, across all offender age groups, most serious 

violent and simple assault victimizations committed by 

adolescents were committed against an acquaintance or 

stranger. When adolescents committed domestic violence, 

they usually offended alone. About 18% of serious violent 

victimizations and 8% of simple assaults committed by 

adolescents who acted alone were perpetrated against 

a current or former intimate partner or family member 

(table 12).

A greater percentage of serious victimizations committed by 

adolescents who acted alone (48%) or with other adolescents 

(42%) were perpetrated against well-known or casual 

acquaintances than those committed by adolescents who 

co-offended with young adults (21%). Most (67%) serious 

victimizations committed by adolescents who co-offended 

with young adults were perpetrated against strangers. 

Strangers were victims in a greater percentage of serious 

violent victimizations committed by groups of adolescents 

(56%) than adolescents who acted alone (33%). The pattern 

of differences for victim–offender relationships across 

co-offending status were generally similar for simple assault 

and serious violent victimizations during 2004–13.

Table 12

Percent of violent victimizations committed by adolescents, by type of crime, victim–offender relationship, and co-offending 

status, 2004–13

Type of crime and victim–offender relationship Acted alone* Acted with adolescents Acted with young adults

Serious violent victimizationsa

Domestic violenceb 17.9% -- ! 6.3% † !

Well-known or casual acquaintance violence 47.5 42.4% 21.4 †

Stranger violence 32.7 55.7 † 66.7 †

Average annual serious violent victimizationsa 183,600 78,100 † 59,200 †

Simple assault victimizations

Domestic violenceb 8.4% 0.9% † ! 0.5% † !

Well-known or casual acquaintance violence 63.4 60.4 36.1 †

Stranger violence 26.9 35.8 † 59.6 †

Average annual simple assault victimizations 610,400 190,100 † 66,900 †

Note: Detail may not sum to total due to rounding and missing data. For this report, adolescents are persons ages 12 to 17 and young adults are persons ages 18 to 29. 

See appendix table 13 for standard errors. 

*Comparison group.

†Significant difference from comparison group at the 95% confidence interval. 

‡Significant difference from comparison group at the 90% confidence interval.

! Interpret with caution. Estimate is based on 10 or fewer sample cases, or coefficient of variation is greater than 50%.

--Less than 0.05%.

aIncludes rape or sexual assault, robbery, and aggravated assault. 

bIncludes current or former intimate partners, immediate family members, and other relatives.

Source: Bureau of Justice Statistics, National Crime Victimization Survey, 2004–13.
CO-OFFENDING AMONG ADOLESCENTS IN VIOLENT VICTIMIZATIONS, 2004–13 | JULY 2016 9

Adolescents were generally more likely to victimize 

other adolescents than older persons

When adolescents committed serious violent victimizations, 

most victims were also adolescents (table 13). Victims 

were adolescents in 66% of serious violent victimizations 

committed by adolescents who acted alone and in 69% of 

those committed by adolescents who co-offended with other 

adolescents. In comparison, victims were adolescents in 37% 

of serious violence committed by adolescents who acted with 

young adults. Victims were more likely to be male in serious 

violence committed by adolescents who acted with other 

adolescents (64%) or young adults (69%) than by adolescents 

who acted alone (51%).

A greater percentage of serious violent victimizations 

committed by adolescents who acted alone involved white 

victims (63%) than those by adolescents who co-offended 

with other adolescents (48%). A greater percentage of 

victims were black (27%) or Hispanic (23%) in serious 

violence committed by adolescents who co-offended with 

other adolescents than those in which adolescents acted 

alone (15% each). A greater percentage of victims were 

Hispanic in serious violent victimizations committed by 

adolescents who co-offended with young adults (22%) than 

by adolescents who acted alone (15%).

Most adolescent-perpetrated simple assault victimizations 

were committed against other adolescents (table 14). 

Victims were adolescents in the majority of simple assaults 

committed by adolescents who acted alone (76%) or with 

other adolescents (79%). In comparison, victims were 

young adults or older in most victimizations committed by 

adolescents who acted with young adults (64%). A slightly 

greater percentage of victims were male in simple assaults 

committed by adolescents who co-offended with young 

adults (66%) than by those who acted alone (56%). Victim 

race or Hispanic origin distributions were relatively similar 

in simple assaults committed by adolescents who acted 

alone, with other adolescents, and with young adults.

Table 13

Percent of serious violent victimizations committed by 

adolescents, by victim demographic characteristics and 

co-offending status, 2004–13

Victim demographic characteristic

Acted 

alone*

Acted with 

adolescents

Acted with 

young adults

Sex

Male 51.4% 63.6% † 68.6% †

Female 48.6 36.4 † 31.4 †

Race/Hispanic origin

Whitea 62.8% 47.7% † 54.1% ‡

Black/African Americana 15.0 27.1 † 21.2

Hispanic/Latino 14.8 23.2 † 22.2 †

Othera,b 7.3 2.0 † ! 2.5 † !

Age group

Adolescent 66.4% 69.0% 37.3% †

Young adult 10.2 10.7 35.7 †

Adult 23.4 20.3 27.0

Average annual serious 

violent victimizations 183,600 78,100 † 59,200 †

Note: Detail may not sum to total due to rounding and missing data. Serious 

violent victimizations include rape or sexual assault, robbery, and aggravated 

assault. For this report, adolescents are persons ages 12 to 17, young adults are 

persons ages 18 to 29, and adults are persons age 30 or older. See appendix table 

14 for standard errors. 

*Comparison group.

†Significant difference from comparison group at the 95% confidence interval. 

‡Significant difference from comparison group at the 90% confidence interval.

! Interpret with caution. Estimate is based on 10 or fewer sample cases, or 

coefficient of variation is greater than 50%. 

aExcludes persons of Hispanic or Latino origin.

bIncludes American Indian or Alaska Native; Asian, Native Hawaiian, or Other 

Pacific Islander; and persons of two or more races.

Source: Bureau of Justice Statistics, National Crime Victimization Survey, 2004–13.

Table 14

Percent of simple assault victimizations committed by 

adolescents, by victim demographic characteristics and 

co-offending status, 2004–13

Victim demographic characteristic

Acted 

alone*

Acted with 

adolescents 

Acted with 

young adults

Sex

Male 56.4% 55.1% 66.3% ‡

Female 43.6 44.9 33.7 ‡

Race/Hispanic origin

Whitea 66.1% 69.0% 72.5%

Black/African Americana 13.0 13.1 9.3

Hispanic/Latino 14.4 12.3 15.6

Othera,b 6.5 5.6 2.6 † !

Age group

Adolescent 76.0% 78.5% 35.9% †

Young adult 6.7 9.3 33.0 †

Adult 17.3 12.2 † 31.1 †

Average annual simple 

assault victimizations 610,400 190,100 † 66,900 †

Note: Detail may not sum to total due to rounding and missing data. For this 

report, adolescents are persons ages 12 to 17, young adults are persons ages 18 

to 29, and adults are persons age 30 or older. See appendix table 15 for standard 

errors.

*Comparison group.

†Significant difference from comparison group at the 95% confidence interval. 

‡Significant difference from comparison group at the 90% confidence interval.

! Interpret with caution. Estimate is based on 10 or fewer sample cases, or 

coefficient of variation is greater than 50%. 

aExcludes persons of Hispanic or Latino origin.

bIncludes American Indian or Alaska Native; Asian, Native Hawaiian, or Other 

Pacific Islanders; and persons of two or more races.

Source: Bureau of Justice Statistics, National Crime Victimization Survey, 2004–13.
CO-OFFENDING AMONG ADOLESCENTS IN VIOLENT VICTIMIZATIONS, 2004–13 | JULY 2016 10

The adolescent serious violent victimizing rate 

decreased 83% from 1994 to 2013

From 1994 to 2013, the adolescent serious violent 

victimizing rate decreased from 65.5 to 11.4 serious violent 

victimizations per 1,000 adolescents (figure 2). The serious 

violent victimizing rate declined similarly from 1994 to 2013 

for adolescents who acted alone (30.3 victimizations to 4.8 

victimizations per 1,000 adolescents) and adolescents who 

acted with co-offenders of any age (35.2 to 6.6 victimizations 

per 1,000 adolescents, not shown). From 1994 to 2013, the 

serious violent victimizing rate also decreased similarly for 

adolescents who acted with other adolescents (16.8 to 3.1 

victimizations per 1,000 adolescents) and for adolescents 

who acted with young adults (14.6 to 1.6 victimizations per 

1,000 adolescents).

The serious violent victimizing rate also decreased 33% 

from 2004 to 2013. Adolescents committed 17.1 serious 

victimizations per 1,000 adolescents in 2004, compared 

to 11.4 serious victimizations per 1,000 adolescents in 

2013. The decline from 2004 to 2013 was primarily due to 

decreases in serious violence committed by adolescents who 

acted alone (9.1 to 4.8 victimizations per 1,000 adolescents) 

or with young adults (4.1 to 1.6 victimizations per 1,000 

adolescents). The rate of serious violent victimizations 

committed by adolescents who co-offended with other 

adolescents did not change significantly during this period.

From 1994 to 2013, the adolescent simple assault victimizing 

rate decreased 72%, from 139.6 to 38.7 simple assaults per 

1,000 adolescents (figure 3). The simple assault victimizing 

rate declined from 1994 to 2013 more for adolescents 

who acted alone (92.9 to 21.8 simple assaults per 1,000 

adolescents) compared to adolescents who acted with 

co-offenders of any age (46.7 to 16.9 simple assaults per 

1,000 adolescents, not shown). Simple assault victimizing 

rates declined similarly from 1994 to 2013 for adolescents 

who co-offended with other adolescents (27.7 to 11.8 

simple assaults per 1,000 adolescents) and adolescents who 

co-offended with young adults (14.9 to 2.4 simple assaults 

per 1,000 adolescents).

From 2004 to 2013, the simple assault victimizing rate 

decreased 36% among adolescents who acted alone. 

Adolescents who acted alone committed 34.1 victimizations 

per 1,000 in 2004, which decreased to 21.8 simple assaults 

per 1,000 adolescents in 2013. During the same period, 

the rate of simple assaults committed by adolescents who 

co-offended with other adolescents increased 72%, from 

6.9 to 11.8 simple assaults per 1,000 adolescents. The simple 

assault victimizing rate among adolescents who acted with 

young adults did not change significantly from 2004 to 2013.

Figure 2

Serious violent victimizing rates for adolescent offenders, 

by co-offending status, 1994–2013

0

20

40

60

80

Acted with young adults

Acted with adolescents

Acted alone

Total with adolescents

'94 '95 '96 '97 '98 '99 '00 '01 '02 '03 '04 '05 '06 '07 '08 '09 '10 '11 '12 '13

Rate per 1,000 adolescents

Note: Serious violent victimizations include rape or sexual assault, robbery, and 

aggravated assault. Data are based on 2-year rolling averages centered around 

the most recent year beginning in 1993. For this report, adolescents are persons 

ages 12 to 17 and young adults are persons ages 18 to 29. See appendix table 16 

for estimates and standard errors.

Source: Bureau of Justice Statistics, National Crime Victimization Survey, 

1993–2013.

Figure 3

Simple assault victimizing rates for adolescent offenders, 

by co-offending status, 1994–2013

0

30

60

90

120

150

Acted with young adults

Acted with adolescents

Acted alone

Total with adolescents

'94 '95 '96 '97 '98 '99 '00 '01 '02 '03 '04 '05 '06 '07 '08 '09 '10 '11 '12 '13

Rate per 1,000 adolescents

Note: Data are based on 2-year rolling averages centered around the most recent 

year beginning in 1993. For this report, adolescents are persons ages 12 to 17 

and young adults are persons ages 18 to 29. See appendix table 17 for estimates 

and standard errors.

Source: Bureau of Justice Statistics, National Crime Victimization Survey, 

1993–2013.
CO-OFFENDING AMONG ADOLESCENTS IN VIOLENT VICTIMIZATIONS, 2004–13 | JULY 2016 11

Methodology

Survey coverage

The National Crime Victimization Survey (NCVS) is an 

annual data collection conducted by the U.S. Census Bureau 

for the Bureau of Justice Statistics (BJS). The NCVS is a 

self-report survey in which interviewed persons are asked 

about the number and characteristics of victimizations they 

experienced during the prior 6 months. The NCVS collects 

information on nonfatal personal crimes (rape or sexual 

assault, robbery, aggravated assault, simple assault, and 

personal larceny) and household property crimes (burglary, 

motor vehicle theft, and other theft) both reported and not 

reported to police. In addition to providing annual level and 

change estimates on criminal victimization, the NCVS is 

the primary source of information on the nature of criminal 

victimization incidents.

Survey respondents provide information about themselves 

(e.g., age, sex, race and Hispanic origin, marital status, 

education level, and income) and whether they experienced 

a victimization. Information is collected for each 

victimization incident—about the offender (e.g., age, race 

and Hispanic origin, sex, and victim-offender relationship), 

characteristics of the crime (including time and place of 

occurrence, use of weapons, nature of injury, and economic 

consequences), whether the crime was reported to police, 

reasons the crime was or was not reported, and experiences 

with the criminal justice system.

The NCVS is administered to persons age 12 or older from a 

nationally representative sample of households in the United 

States. The survey defines a household as a group of persons 

who reside at a sampled address. Persons are considered 

household members when the sampled address is their 

usual place of residence at the time of the interview and 

when they have no usual place of residence elsewhere. Once 

selected, households remain in the sample for 3 years, and 

eligible persons in these households are interviewed every 

6 months either in person or over the phone for a total of 

seven interviews.

Generally, all first interviews are conducted in-person. New 

households rotate into the sample on an ongoing basis to 

replace outgoing households that have been in the sample for 

a 3-year period. The sample includes persons living in group 

quarters, such as dormitories, rooming houses, and religious 

group dwellings, and excludes persons living in military 

barracks and institutional settings, such as correctional or 

hospital facilities, and individuals who are homeless. (For 

more information, see Survey Methodology for Criminal 

Victimization in the United States, 2008, NCJ 231173, BJS 

web, May 2011.)

Weighting adjustments for estimating personal 

victimization

From 2004 to 2013, an annual average of 144,940 NCVS 

interviews were conducted with persons age 12 or older. The 

response rate was 87% for eligible persons. Response rates 

were lower among adolescents ages 12 to 17 (72%) than 

among young adults ages 18 to 29 (81%) and adults age 30 

or older (90%). Weighting adjustments in the NCVS have 

been found to produce demographic distributions among 

adolescents (including sex, race, number of persons in the 

household) that are comparable to adolescent demographic 

distributions in the American Community Survey.

Victimizations that occurred outside of the United States 

were excluded from this report. On average each year 

from 2004 to 2013, less than 1% of the unweighted violent 

victimizations occurred outside of the United States and 

were excluded from the analyses.

Estimates in this report use data from yearly NCVS data 

files weighted to produce annual estimates of violent 

victimizations for persons age 12 or older living in U.S. 

households. Because the NCVS relies on a sample rather 

than a census of the entire U.S. population, weights are 

designed to inflate sample point estimates to known 

population totals and to compensate for survey nonresponse 

and other aspects of the sample design.

The victimization weights used in this analysis account 

for the number of persons present during an incident and 

for repeat victims of series incidents. The weight counts 

series incidents as the actual number of incidents reported 

by the victim, up to a maximum of 10 incidents. Series 

victimizations are victimizations that are similar in type but 

occur with such frequency that a victim is unable to recall 

each individual event or to describe each event in detail. 

Survey procedures allow NCVS interviewers to identify and 

classify these similar victimizations as series victimizations 

and collect detailed information on only the most recent 

incident in the series. In 2013, about 1% of all victimizations 

and 4% of all violent victimizations were series incidents. 

Weighting series incidents as the number of incidents up 

to a maximum of 10 produces more reliable estimates of 

crime levels, while the cap at 10 minimizes the effect of 

extreme outliers on the rates. Additional information on 

the series enumeration is detailed in Methods for Counting 

High Frequency Repeat Victimizations in the National Crime 

Victimization Survey (NCJ 237308, BJS web, April 2012).
CO-OFFENDING AMONG ADOLESCENTS IN VIOLENT VICTIMIZATIONS, 2004–13 | JULY 2016 12

Limitations of using the NCVS to calculate victimizing 

rates by age of offender

Limitations to calculating violent victimizing rates by age 

of the offender using data from the NCVS include missing 

respondent data, bias in survey coverage, and differences 

in survey response rates by respondent age. This report is 

based on victimizations in which the victim provided an 

estimate of the offenders’ age. For the period 2004 to 2013, 

victims did not provide estimates of offender age in 12% 

of the total violent victimizations they reported. Available 

data suggest that offenders tend to be close in age to their 

victims. In 2004–13, there was no measurable difference in 

the percentage of missing data on offender age for adolescent 

victims compared to older victims. Data on offender age 

were missing for 12% of victimizations committed against 

adolescents ages 12 to 17, 12% of victimizations committed 

against young adults ages 18 to 29, and 11% of victimizations 

committed against adults age 30 or older.

This report is also based on victimizations committed by 

at least one person age 12 or older, and excludes about 

1% of total violent victimizations against persons age 12 

or older that were committed solely by persons age 11 or 

younger in 2004–13. These victimizations were excluded 

due to insufficient sample sizes and because by design the 

NCVS survey coverage does not include children age 11 and 

younger. NCVS data likely underestimate the number of 

victimizations committed by children age 11 and younger 

because the most likely victims of these crimes (i.e., children 

age 11 and younger) are excluded from the NCVS sample. 

Similarly, NCVS data likely underestimate the number of 

adolescent offenders ages 12 to 14 because some of their 

victims (children age 11 and younger) are excluded from the 

NCVS sample.

The NCVS allows for comparisons between adolescent 

offenders ages 12 to 14 and 15 to 17, but small sample sizes 

and missing information about co-offenders complicate 

these analyses. Grouping offender age into more categories 

resulted in insufficient sample sizes to examine many 

questions of interest. In victimizations committed by 

multiple offenders, it was not always clear whether 

adolescents ages 15 to 17 were involved as offenders. For 

example, victims might have reported the youngest offender 

to be age 12 to 14 and the oldest offender to be age 18 to 20. 

In this scenario, it would not be known if one or more of the 

offenders were ages 15 to 17. In addition, victims report their 

perceptions of the offender’s age. In some victimizations, 

particularly those committed by strangers, victims might 

inaccurately classify the age of the offender.

Calculating victimizing rates by age of offenders is further 

complicated by missing data on the age of all co-offenders. 

Respondents are asked to estimate the age of the oldest and 

youngest offender. If the youngest offender was reported to 

be age 11 or younger and the oldest offender was reported 

to be age 18 or older, the involvement of an adolescent age 

12 to 17 is unknown. In 2004–13, this made up less than 

0.5% of violent victimizations. During the same period, 

0.5% of victimizations were reported to be committed 

by the youngest offenders (ages 12 to 17) acting with an 

oldest offender age 30 or older. Therefore, it was not known 

whether a young adult age 18 to 29 was involved.

Offender race and Hispanic origin in the NCVS

In 2012, BJS changed the manner in which the NCVS 

collects information about the perceived race of offender. 

These changes were made to be consistent with the Office 

of Management and Budget’s Standards for the Classification 

of Federal Data on Race and Ethnicity that specify the 

minimum number of categories for statistical reporting 

on race.

Information on an offender’s race and Hispanic origin is 

collected from the victim, therefore, it is what the victim 

perceived it to be. Prior to 2012, the NCVS collected 

offender race as white, black or African American, other 

race, and don’t know. In 2012, offender race categories were 

expanded to include American Indian or Alaska Native; or 

Asian, Native Hawaiian, or Other Pacific Islander. In 2012, 

the NCVS also began collecting information on whether the 

offender was of Hispanic or Latino origin.

Table 6 in this report includes information on the perceived 

race of offender. The “other race” category in this table 

includes offenders of other races from 2004–11 but also 

includes offenders who were American Indian or Alaska 

Native; or Asian, Native Hawaiian, or Other Pacific Islander 

from 2012–13. Respondents were also asked if the offender 

was of Hispanic or Latino origin. However, since it cannot 

be determined if an offender was of Hispanic and Latino 

origin prior to 2012, this category was excluded from the 

analysis for 2012 and 2013. Hispanic or Latino persons were 

grouped into their racial category or categories perceived by 

the victim. Single offenders of two or more races were also 

included in 2012 and 2013.

The “multiple offenders of various races” category in table 6 

includes multiple offenders of different races. Prior to 2012, 

this included white, black or African American, and other 

race. In 2012 and 2013, this included white; black or African 

American; American Indian or Alaska Native; and Asian, 

Native Hawaiian, or Other Pacific Islander.
CO-OFFENDING AMONG ADOLESCENTS IN VIOLENT VICTIMIZATIONS, 2004–13 | JULY 2016 13

Standard error computations

When national estimates are derived from a sample, as with 

the NCVS, caution must be taken when comparing one 

estimate to another or when comparing estimates over time. 

Although one estimate may be larger than another, estimates 

based on a sample have some degree of sampling error. The 

sampling error of an estimate depends on several factors, 

including the amount of variation in the responses and the 

size of the sample. When the sampling error around an 

estimate is taken into account, the estimates that appear to 

be different may not be statistically different.

The standard error is one measure of the sampling error 

associated with an estimate and can vary from one estimate 

to the next. Generally, an estimate with a small standard 

error provides a more reliable approximation of the true 

value than an estimate with a large standard error. Estimates 

with relatively large standard errors are associated with 

less precision and reliability and should be interpreted 

with caution.

To generate standard errors around numbers and estimates 

from the NCVS, the Census Bureau produced generalized 

variance function (GVF) parameters for BJS. The GVFs take 

into account aspects of the NCVS complex sample design 

and represent the curve fitted to a selection of individual 

standard errors based on the Jackknife Repeated Replication 

technique. The GVF parameters were used to generate 

standard errors for each point estimate (such as counts, 

percentages, and rates) in this report.

BJS conducted tests to determine whether differences in 

estimated numbers and percentages in this report were 

statistically significant once sampling error was taken into 

account. Using statistical programs developed specifically 

for the NCVS, all comparisons in the text were tested 

for significance. The Student’s t-statistic was the primary 

test procedure, which tests the difference between two 

sample estimates.

Data users can use the estimates and the standard errors of 

the estimates provided in this report to generate a confidence 

interval around the estimate as a measure of the margin of 

error. The following example illustrates how standard errors 

can be used to generate confidence intervals:

In 2004 to 2013, according to the NCVS, the rate of 

nonfatal violent victimization committed by adolescent 

offenders ages 12 to 17 was 50.0 victimizations per 1,000 

adolescents (see figure 1). Using the GVFs, the estimate 

has a standard error of 2.3 (see appendix table 1). A 

confidence interval around the estimate was generated by 

multiplying +/- 1.96 (the t-score of a normal, two-tailed 

distribution that excludes 2.5% at either end of the 

distribution). Therefore, the 95% confidence interval 

around the 50.0 estimate from 2004 to 2013 is 50.0 +/- 

(2.3 × 1.96) or (45.5 to 54.5). In other words, if different 

samples using the same procedure were taken from the 

U.S. population from 2004 to 2013, 95% of the time 

the rate of nonfatal violent victimization committed by 

adolescent offenders ages 12 to 17 would be between 45.5 

and 54.5 victimizations per 1,000 adolescents.

In this report, BJS also calculated a coefficient of variation 

(CV) for all estimates, representing the ratio of the standard 

error to the estimate. CVs provide a measure of reliability 

and a means for comparing the precision of estimates across 

measures with differing levels or metrics. When the CV 

was greater than 50%, or the unweighted sample had 10 or 

fewer cases, the estimate was noted with an exclamation 

point (! Interpret data with caution. Estimate based on 10 or 

fewer sample cases, or the coefficient of variation is greater 

than 50%).
CO-OFFENDING AMONG ADOLESCENTS IN VIOLENT VICTIMIZATIONS, 2004–13 | JULY 2016 14

Appendix table 1

Estimates and standard errors for figure 1: Violent victimizing rates, by offender age group and co-offending status, 2004–13

Adolescents* Young adults Adults

Rate Standard error Rate Standard error Rate Standard error

Total 50.0 2.30 45.2 ‡ 1.75 13.7 † 0.55

Offenders who acted alone 31.8 1.71 32.2 1.40 11.8 † 0.49

Offenders who acted with co-offenders 18.1 1.19 12.9 † 0.77 1.9 † 0.14

Note: Violent victimizations include rape or sexual assault, robbery, aggravated assault, and simple assault. Victimizing rates are calculated as the number of 

victimizations committed by a specific age group divided by the total population of that age group.

*Comparison group.

†Significant difference from comparison group at the 95% confidence interval. 

‡Significant difference from comparison group at the 90% confidence interval.

Source: Bureau of Justice Statistics, National Crime Victimization Survey, 2004–13.

Appendix table 2

Standard errors for table 1: Percent of total violent 

victimizations, by offender age group, 2004–13

Offender age group

Average annual 

victimizations

Percent 

of total

Percent committed 

by persons ages 

12 or oldera

Violent victimizations 

committed by persons 

ages 12 or older 359,384 0.78%

Any adolescent 131,344 0.77 0.86%

Any young adult 194,611 1.00 1.09

Any adult 203,580 1.03 1.11

All children under age 12 23,975 0.14 ~

Unknown ages 94,067 0.58 ~

Total violent 

victimizations 352,541 

~Not applicable.

Source: Bureau of Justice Statistics, National Crime Victimization Survey, 2004–13.

Appendix table 3

Standard errors for table 2: Percent of violent victimizations 

committed by adolescents, by co-offending status, 2004–13

Adolescent co-offending status Percent

All violent victimizations

Acted alone 1.80%

Acted with co-offenders 1.70

All violent victimizations involving co-offenders

All co-offenders age 17 or younger 2.55%

At least one age 11 or younger 0.79

All ages 12–17 2.58

Oldest co-offender age 18 or older 2.39

Ages 18–29 2.21

Age 30 or older 1.08

Average annual violent victimizations 131,344

Source: Bureau of Justice Statistics, National Crime Victimization Survey, 2004–13.
CO-OFFENDING AMONG ADOLESCENTS IN VIOLENT VICTIMIZATIONS, 2004–13 | JULY 2016 15

Appendix table 5

Standard errors for table 4: Percent of co-offenders involved 

in violent victimizations, by age of oldest and youngest 

offenders, 2004–13

Age of youngest offender

Age of oldest offender 12–14 15–17 18–20 21–29

30 or 

older

12–14 3.49% ~ ~ ~ ~

15–17 3.37 3.22% ~ ~ ~

18–20 1.32 3.05 2.95% ~ ~

21–29 0.84 2.00 3.20 3.12% ~

30 or older 1.61 1.41 2.63 2.97 ~

Average annual 

violent victimizations 41,533 46,170 46,452 49,727 32,859

~Not applicable.

Source: Bureau of Justice Statistics, National Crime Victimization Survey, 2004–13.

Appendix table 6

Standard errors for table 5: Percent of adolescents who 

co-offended with young adults, by age of youngest and 

oldest offenders, 2004–13

Age of oldest offender

Age of youngest offender 18–20 21–29 18–29

12–14 2.73% 4.49% 2.42%

15–17 3.05 4.84 2.73

Average annual 

violent victimizations 26,450 15,205 31,818

Source: Bureau of Justice Statistics, National Crime Victimization Survey, 2004–13.

Appendix table 4

Standard errors for table 3: Percent of violent victimizations, 

by offender age group and co-offending status, 2004–13

Offender age group and 

co-offending status

Average annual 

victimizations

Percent 

of total

Violent victimizations committed by 

persons ages 12 or older 359,384

Adolescents who—

Acted alone 97,989 0.67%

Acted only with adolescents 49,864 0.36

Acted with young adults 31,818 0.22

Young adults who—

Acted alone 155,370 0.96%

Acted with young adults or adults 72,351 0.51

Adults who—

Acted alone 184,099 1.06%

Acted with adults 32,859 0.23

Other 31,841 0.22

Source: Bureau of Justice Statistics, National Crime Victimization Survey, 2004–13.

Appendix table 8

Standard errors for table 7: Percent of violent victimizations 

committed by adolescents who co-offended, by number of 

co-offenders and gang status, 2004–13

Acted with 

adolescents

Acted with 

young adults

Number of offenders

Two 3.07% 2.90%

Three 2.53 3.38

Four or more 2.68 4.20

Gang status

Yes 2.29% 3.59%

No 3.01 3.39

Don’t know 3.06 4.20

Average annual violent victimizations 49,864 31,818

Source: Bureau of Justice Statistics, National Crime Victimization Survey, 2004–13.

Appendix table 7

Standard errors for table 6: Percent of violent victimizations 

committed by adolescents, by offender demographic 

characteristics and co-offending status, 2004–13

Offender demographic characteristic

Acted 

alone

Acted with 

adolescents 

Acted with 

young adults

Sex

Male 1.97% 3.09% 4.10%

Female 1.80 2.62 2.30

Male and female ~ 1.75 3.52

Race

White 2.12% 3.12% 3.76%

Black/African American 1.74 2.70 4.04

Other race 1.14 0.90 2.15

Offenders of multiple races ~ 1.93 3.09

Don’t know 0.71 1.29 0.60

Average annual 

violent victimizations 97,989 49,864 31,818

~Not applicable.

Source: Bureau of Justice Statistics, National Crime Victimization Survey, 2004–13.

Appendix table 9

Standard errors for table 8: Percent of violent victimizations 

committed by adolescents, by type of crime and 

co-offending status, 2004–13

Type of crime

Acted 

alone

Acted with 

adolescents

Acted with 

young adults

Serious violent victimizations 1.23% 2.02% 3.08%

Robbery 0.79 1.97 2.80

Aggravated assault 0.96 1.18 2.64

Simple assault victimizations 1.80% 2.82% 4.06%

Average annual serious violent 

victimizations 29,257 17,760 15,170

Average annual simple 

assault victimizations 79,979 39,102 21,299

Source: Bureau of Justice Statistics, National Crime Victimization Survey, 2004–13.
CO-OFFENDING AMONG ADOLESCENTS IN VIOLENT VICTIMIZATIONS, 2004–13 | JULY 2016 16

Appendix table 10

Standard errors for table 9: Percent of serious violent 

victimizations committed by adolescents involving a 

weapon, by co-offending status, 2004–13

Weapon use

Acted 

alone

Acted with 

adolescents

Acted with 

young adults

Yes 2.64% 3.76% 3.91%

No 2.48 3.66 3.53

Don’t know 0.90 1.97 1.62

Average annual serious violent 

victimizations involving a weapon 21,940 12,035 12,466

Average annual serious 

violent victimizations 29,257 17,760 15,170

Source: Bureau of Justice Statistics, National Crime Victimization Survey, 2004–13.

Appendix table 11

Standard errors for table 10: Percent of serious violent 

victimizations committed by adolescents involving injury, by 

injury type and co-offending status, 2004–13

Victim injury

Acted 

alone

Acted with 

adolescents

Acted with 

young adults

Yes 2.42% 3.37% 4.11%

Serious injuries 1.76 1.43 3.01

Bruises, cuts, or other minor injuries 1.88 3.17 3.49

No 2.56% 3.52% 4.18%

Average annual serious violent 

victimizations involving an injury 15,169 9,137 9,251

Average annual serious 

violent victimizations 29,257 17,760 15,170

Source: Bureau of Justice Statistics, National Crime Victimization Survey, 2004–13.

Appendix table 12

Standard errors for table 11: Percent of violent victimizations committed by adolescents that were reported to police, by type 

of crime and co-offending status, 2004–13

Acted alone Acted with adolescents Acted with young adults

Serious violent victimizations reported to police

Yes 2.65% 3.76% 3.90%

No 2.68 3.75 3.67

Average annual serious violent victimizations reported to police 18,690 12,093 12,501

Average annual serious violent victimizations 29,257 17,760 15,170

Simple assault victimizations reported to police

Yes 1.82% 3.17% 5.21%

No 2.05 3.34 5.25

Average annual simple assault victimizations reported to police 34,097 20,747 13,741

Average annual simple assault victimizations 79,979 39,102 21,299

Source: Bureau of Justice Statistics, National Crime Victimization Survey, 2004–13.

Appendix table 13

Standard errors for table 12: Percent of violent victimizations committed by adolescents, by type of crime, victim–offender 

relationship, and co-offending status, 2004–13

Type of crime and victim–offender relationship Acted alone Acted with adolescents Acted with young adults

Serious violent victimizations

Domestic violence 1.91% ~ 1.88%

Well-known or casual acquaintance violence 2.66 3.68% 3.33

Stranger violence 2.44 3.76 4.03

Average annual serious violent victimizations 29,257 17,760 15,170

Simple assault victimizations

Domestic violence 1.06% 0.51% 0.63%

Well-known or casual acquaintance violence 2.21 3.42 4.96

Stranger violence 1.88 3.24 5.19

Average annual simple assault victimizations 79,979 39,102 21,299

~Not applicable.

Source: Bureau of Justice Statistics, National Crime Victimization Survey, 2004–13.
CO-OFFENDING AMONG ADOLESCENTS IN VIOLENT VICTIMIZATIONS, 2004–13 | JULY 2016 17

Appendix table 14

Standard errors for table 13: Percent of serious violent 

victimizations committed by adolescents, by victim 

demographic characteristics and co-offending status, 

2004–13

Victim demographic characteristic

Acted 

alone

Acted with 

adolescents 

Acted with 

young adults

Sex

Male 2.67% 3.66% 3.98%

Female 2.66 3.56 3.83

Race/Hispanic origin

White 2.62% 3.75% 4.22%

Black/African American 1.76 3.24 3.31

Hispanic/Latino 1.75 3.05 3.38

Other 1.23 0.91 1.16

Age group

Adolescent 2.57% 3.54% 4.03%

Young adult 1.46 2.15 3.98

Adult 2.15 2.89 3.64

Average annual serious 

violent victimizations 29,257 17,760 15,170

Source: Bureau of Justice Statistics, National Crime Victimization Survey, 2004–13.

Appendix table 15

Standard errors for table 14: Percent of simple assault 

victimizations committed by adolescents, by victim 

demographic characteristics and co-offending status, 

2004–13

Victim demographic characteristic

Acted 

alone

Acted with 

adolescents

Acted with 

young adults

Sex

Male 2.25% 3.45% 5.03%

Female 2.20 3.41 4.87

Race/Hispanic origin

White 2.18% 3.26% 4.77%

Black/African American 1.34 2.13 2.82

Hispanic/Latino 1.41 2.06 3.60

Other 0.92 1.38 1.48

Age group

Adolescent 1.99% 2.92% 4.95%

Young adult 0.94 1.80 4.84

Adult 1.54 2.06 4.75

Average annual simple 

assault victimizations 79,979 39,102 21,299

Source: Bureau of Justice Statistics, National Crime Victimization Survey, 2004–13.
CO-OFFENDING AMONG ADOLESCENTS IN VIOLENT VICTIMIZATIONS, 2004–13 | JULY 2016 18

Appendix table 16

Rates and standard errors for figure 2: Serious violent victimizing rates for adolescent offenders, by co-offending status, 

1993–2013

Rate per 1,000 adolescents Standard errors

Year

Total with 

adolescents Acted alone

Acted with 

adolescents

Acted with 

young adults

Total with 

adolescents Acted alone

Acted with 

adolescents

Acted with 

young adults

1994 65.5 30.3 16.8 14.6 3.83 2.38 1.65 1.52

1995 57.0 24.4 13.1 16.8 3.49 2.05 1.39 1.62

1996 49.1 20.9 12.2 13.8 3.13 1.81 1.28 1.38

1997 46.4 21.7 11.9 10.4 3.36 2.06 1.40 1.29

1998 40.3 19.6 9.5 8.9 3.33 2.08 1.30 1.25

1999 36.2 17.9 8.9 7.3 3.09 1.95 1.23 1.08

2000 30.0 15.5 7.5 5.4 2.75 1.78 1.12 0.90

2001 23.7 13.3 4.5 4.5 2.27 1.56 0.78 0.78

2002 20.8 9.6 4.8 4.3 2.21 1.34 0.85 0.79

2003 18.3 8.3 4.0 4.4 2.05 1.22 0.75 0.80

2004 17.1 9.1 2.9 4.1 1.83 1.23 0.60 0.74

2005 16.0 8.4 3.6 3.2 1.74 1.16 0.68 0.64

2006 16.6 9.8 3.0 3.2 1.69 1.20 0.58 0.59

2007 14.7 8.7 2.0 3.1 1.59 1.12 0.43 0.57

2008 16.0 9.4 2.5 3.0 1.81 1.27 0.55 0.61

2009 16.7 9.3 4.6 2.2 2.15 1.49 0.96 0.61

2010 13.6 6.5 4.8 2.2 1.82 1.11 0.92 0.55

2011 9.6 5.4 2.3 1.6 1.40 0.96 0.55 0.43

2012 9.3 4.5 2.5 1.4 1.26 0.81 0.55 0.39

2013 11.4 4.8 3.1 1.6 1.45 0.83 0.63 0.43

Source: Bureau of Justice Statistics, National Crime Victimization Survey, 1993–2013.

Appendix table 17

Rates and standard errors for figure 3: Simple assault victimizing rates for adolescent offenders, by co-offending status, 

1993–2013

Rate per 1,000 adolescents Standard errors

Year

Total with 

adolescents Acted alone

Acted with 

adolescents

Acted with 

young adults

Total with 

adolescents Acted alone

Acted with 

adolescents

Acted with 

young adults

1994 139.6 92.9 27.7 14.9 6.63 5.25 2.51 1.70

1995 136.0 87.5 27.1 15.3 5.92 4.58 2.21 1.54

1996 117.6 75.9 24.6 10.5 5.61 4.30 2.10 1.22

1997 110.1 76.2 20.0 9.1 5.96 4.76 2.03 1.22

1998 98.7 69.7 15.2 9.7 6.70 5.40 2.02 1.51

1999 87.8 60.1 15.0 9.9 6.04 4.76 1.93 1.47

2000 71.3 49.2 13.4 6.3 5.42 4.28 1.84 1.12

2001 58.6 41.3 10.7 4.2 4.46 3.57 1.49 0.82

2002 55.7 41.7 9.2 3.5 4.68 3.88 1.44 0.77

2003 53.0 39.4 8.7 2.9 4.51 3.72 1.37 0.67

2004 46.1 34.1 6.9 2.8 3.84 3.17 1.14 0.65

2005 43.6 32.4 7.1 2.7 3.67 3.04 1.16 0.64

2006 45.0 31.3 9.2 3.5 3.50 2.78 1.27 0.69

2007 42.3 30.5 8.1 2.6 3.41 2.75 1.13 0.53

2008 38.3 28.3 6.3 2.9 3.44 2.82 1.05 0.63

2009 32.4 20.1 6.8 3.8 3.47 2.56 1.29 0.90

2010 24.0 14.3 5.3 2.9 2.74 1.95 1.01 0.68

2011 24.2 16.8 4.2 1.9 2.57 2.02 0.80 0.48

2012 32.7 20.8 7.3 2.4 2.75 2.06 1.06 0.53

2013 38.7 21.8 11.8 2.4 3.63 2.50 1.68 0.60

Source: Bureau of Justice Statistics, National Crime Victimization Survey, 1993–2013.
Office of Justice Programs

Innovation • Partnerships • Safer Neighborhoods

www.ojp.usdoj.gov

NCJ 249756

The Bureau of Justice Statistics of the U.S. Department of Justice is the principal 

federal agency responsible for measuring crime, criminal victimization, criminal 

offenders, victims of crime, correlates of crime, and the operation of criminal 

and civil justice systems at the federal, state, tribal, and local levels. BJS collects, 

analyzes, and disseminates reliable and valid statistics on crime and justice 

systems in the United States, supports improvements to state and local criminal 

justice information systems, and participates with national and international 

organizations to develop and recommend national standards for justice statistics. 

Jeri M. Mulrow is acting director.

This report was written by Barbara A. Oudekerk and Rachel E. Morgan, BJS 

Statisticians. Erika Harrell verified the report.

Lynne McConnell and Jill Thomas edited the report, and Barbara Quinn produced 

the report.

July 2016, NCJ 249756