Defining and Calculating Dropout and Completion Rates Using the CPS

Event Dropout Rates

The October Supplement to the CPS is the only national data source that currently can be used to estimate annual national dropout rates. As a measure of recent dropout experiences, the event dropout rate measures the proportion of students who dropped out over a 1–year interval.

The numerator of the event dropout rate for October 2005 is the number of persons 15–24 years old surveyed in 2005 who were enrolled in grades 10–12 in October 2004, were not enrolled in high school in October 2005, and who also did not complete high school (that is, had not received a high school diploma or an alternative credential such as an equivalency certificate) between October 2004 and October 2005.

The denominator of the event dropout rate for 2005 is the sum of the dropouts (that is, the numerator) and all persons 15–24 years old who were attending grades 10–12 in October 2004, who were still enrolled in October 2005, or who graduated or completed high school between October 2004 and October 2005.

The dropout interval is defined to include the previous summer (in this case, the summer of 2005) and the previous school year (in this case, the 2004 school year), so that once a grade is completed, the student is then at risk of dropping out of the next grade. Given that the data collection is tied to each person’s enrollment status in October of 2 consecutive years, any student who drops out and returns within the 12–month period is not counted as a dropout.

Status Dropout Rates

The status dropout rate reflects the percentage of individuals who are dropouts, regardless of when they dropped out. The numerator of the status dropout rate for 2005 is the number of individuals ages 16–24 years who, as of October 2005, had not completed high school and were not currently enrolled. The denominator is the total number of 16– through 24–year–olds in October 2005.

Status Completion Rates

The numerator of the high school status completion rate is the number of 18– through 24–year–olds who had received a high school diploma or an alternative credential such as an equivalency certificate. The denominator is the number of 18– through 24–year–olds who are no longer in elementary or secondary school.

GED Credentials and the Status Completion Rate. Prior to 2000, editions of this series of dropout reports presented estimates of overall status completion rates and estimates of the method of completion—graduation by diploma or completion by taking an alternative exam such as the GED test. Examination of the changes in the CPS GED items in the October 2000 and subsequent surveys has indicated that GED estimates for 2000 and later years are not comparable with earlier data and may not be reliable estimates of high school equivalency completions (table A–1). Therefore, CPS estimates of the method of high school completion have not been presented in recent dropout reports. Because the method of high school completion remains of interest, an estimate of those who passed the GED exam using GED Testing Service (GEDTS) data was developed.

Data on GED testing are collected by the GEDTS and reported in a series of annual statistical reports (American Council on Education, GED Testing Service 1991–2006). These reports indicate the number of people passing the GED test, by age group. Tabulation of data presented in GEDTS reports from 1998 through 2004 permits an estimate of the number of persons ages 18–24 in 2004 (the most recent year for which data are available) who ever passed the GED test. The source data from the GEDTS reports are presented in table A–2.

GEDTS reports present the number of GED passers²⁶ in the United States and the percentage of passers in each age group for persons ages 16 (or age 16 and younger²⁷), 17, 18, 19, 20–24, and higher age groups. The number of people in 2004 who were ages 18–24 and who passed the GED test equals the sum of the number of people who passed the GED test since 1998 at specific ages. The GEDTS reports present grouped data for persons ages 20–24. As a result, a count of the number of passers at each specific age from 20 through 24 is not available. Analysis of GEDTS data on GED passers from 2001 and 2002 indicates that approximately 8 percent of all GED passers are age 20, 6 percent are age 21, 5 percent are age 22, 4 percent are age 23, and 3 percent are age 24 (data not shown in tables).

Data Considerations for CPS

Over the last several decades, data collection procedures, items, and data preparation processes have changed in the CPS. Some of these changes were introduced to ensure CPS estimates were comparable to decennial Census collections, some were introduced to reflect changes in the concepts under study, some were introduced to improve upon measures, and some were introduced to develop measures for new phenomena. The effects of the various changes have been studied to help ensure they did not disrupt trend data from CPS. For a summary of these studies, please see appendix C of Dropout Rates in the United States: 2001 (Kaufman, Alt, and Chapman 2004).

CPS data include weights to help make estimates from the data representative of the civilian, noninstitutionalized population in the United States. These weights are based on decennial Census data that are adjusted for births, deaths, immigration, emigration, etc., over time.

Imputation for Item Nonresponse in CPS. For many key items in the October CPS, the U.S. Census Bureau imputes data for cases with missing data due to item nonresponse. However, the Census Bureau did not impute data regarding the method of high school completion before 1997. Special imputations were conducted for these items using a sequential hot deck procedure implemented through the PROC IMPUTE computer program developed by the American Institutes for Research. Three categories of age, two categories of race, two categories of sex, and two categories of citizenship were used as imputation cells.

Age and Grade Ranges in CPS Estimates. The age and grade ranges used in the CPS measures of dropout rates are constrained by available data. Ideally, the estimates would be able to capture reliable estimates of children in grades as low as grade 9. However, the CPS asks the question about enrollment the previous October only about individuals age 15 and older. Many 9th–graders are younger than age 15, so 10th grade was selected as the lower boundary of grade ranges in the event dropout rate.

Accuracy of CPS Estimates. CPS estimates in this report are derived from samples and are subject to two broad classes of error—sampling and nonsampling error. Sampling errors occur because the data are collected from a sample of a population rather than from the entire population. Estimates based on a sample will differ somewhat from the values that would have been obtained from a universe survey using the same instruments, instructions, and procedures. Nonsampling errors come from a variety of sources and affect all types of surveys—universe as well as sample surveys. Examples of sources of nonsampling error include design, reporting, and processing errors and errors due to nonresponse. The effects of nonsampling errors are more difficult to evaluate than those that result from sampling variability. As much as possible, procedures are built into surveys in order to minimize nonsampling errors.

The standard error is a measure of the variability due to sampling when estimating a parameter. It indicates how much variance there is in the population of possible estimates of a parameter for a given sample size. Standard errors can be used as a measure of the precision expected from a particular sample. The probability that a sample statistic would differ from a population parameter by less than the standard error is about 68 percent. The chances that the difference would be less than 1.65 times the standard error are about 90 out of 100; and that the difference would be less than 1.96 times the standard error, about 95 out of 100.

Standard errors for percentages and number of persons based on CPS data were calculated using the following formulas:

Percentage:

	se	=
where	p	=	the percentage (0 < p < 100),
	N	=	the population on which the percentage is based, and
	b	=	the regression parameter based on a generalized variance formula and is associated with the characteristic. For 2005, b is equal to 2,131 for the total or White population, 2,410 for the Black population, 2,744 for the Hispanic population, and 2,410 for the Asian/Pacific Islander or “more than one race” populations ages 14–24. The b for regional estimates are: 0.90 for the Northeast, 0.93 for the Midwest, 1.14 for the South, and 1.14 for the West

CPS documentation explains the purpose and process for the generalized variance parameter:

Experience has shown that certain groups of estimates have similar relations between their variances and expected values. Modeling or generalizing may provide more stable variance estimates by taking advantage of these similarities. The generalized variations function is a simple model that expresses the variance as a function of the expected value of a survey estimate. The parameters of the generalized variance function are estimated using direct replicate variances. (Cahoon 2005, p. 7)

Number of persons:

	se	=
where	x	=	the number of persons (i.e., dropouts),
	T	=	population in the category (e.g., Blacks ages 16–24), and
	b	=	as above.

Top

---

²⁶ Passing the GED is a good but imperfect indicator of receiving a high school equivalency credential. Some people who pass the test may not receive the credential because they do not file necessary paperwork or pay necessary fees. People may also leave the country, die, or receive a regular high school diploma after passing the GED test. Furthermore, some states grant equivalency credentials that are not based on the GED test.
²⁷ The lowest standard minimum age for testing in any state is 16. Some jurisdictions grant exceptions to the minimum age on a case–by–case basis. GEDTS reports from 1996 to 1998 group the small number of individuals under age 16 as 16 years old for reporting purposes.