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Dropout and Completion Rates in the United States: 2006

NCES 2008-053
September 2008

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 2006 is the number of persons ages 15–243 surveyed in October 2006 who were enrolled in grades 10–12 in October 2005, who were not enrolled in high school in October 2006, 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 2005 and October 2006.

The denominator of the event dropout rate for 2006 is the sum of the dropouts (that is, the numerator) and all persons ages 15–24 who were attending grades 10–12 in October 2005, who were still enrolled in October 2006, or who graduated or completed high school between October 2005 and October 2006.

The dropout interval is defined to include the previous summer (in this case, the summer of 2006) and the previous school year (in this case, the 2005 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 2006 is the number of individuals ages 16–244 who, as of October 2006, had not completed high school and were not currently enrolled. The denominator is the total number of 16- through 24-year-olds in October 2006.

Status Completion Rates

The numerator of the high school status completion rate is the number of 18- through 24-year-olds5 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. Examination of the changes in the CPS GED items in the October 2000 and subsequent surveys has indicated that GED estimates may not be reliable estimates of high school equivalency completions.6 Therefore, CPS estimates of the method of high school equivalency 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 (table A-2).

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 1991–2002, 2003–06, 2007). These reports indicate the number of people passing the GED test, by age group. Tabulation of data presented in GEDTS reports from 1998 through 2007 permits an estimate of the number of persons ages 18–24 in 2006 (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.

The GED Testing Service reports the number of people who passed the GED exam each year by age. Their most recent report indicates that approximately 209,000 18- to 24-year-olds passed the GED in 2006. In order to determine how many 18- to 24-year-olds held a GED in 2006, and not the number who earned the GED that year alone, data from several reports had to be combined. This was done by adding the count of 18- to 24-year-olds who passed the exam in 2006 to counts of people who were ages 18–24 in 2006, but who passed the exam in earlier years. The number of 18- to 24-year-olds who passed the exam in 2006 was added to the number of 17- to 23-year-olds who passed the exam in 2005. That sum was added to the number of 16- to 22- year-olds who passed the exam in 2004, the number of 16- to 21-year-olds who passed the exam in 2003, the number of 16- to 20-year-olds who passed the exam in 2002, the number of 16- to 19-year-olds who passed the exam in 2001, the number of 16- to 18-year-olds who passed the exam in 2000, the number of 16- and 17-year-olds who passed the exam in 1999, and the number of 16-year-olds who passed the exam in 1998. Sixteen year-olds in 1998 would have been 24 in 2006. The lowest standard minimum age for testing in any state is 16. It is important to note that work done independently by Mishel and Roy (2006) led them to the same approach of estimating counts of GED holders among young adults.

Data Considerations for the 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 that CPS estimates were comparable to those from 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 do not disrupt trend data from the CPS. For a summary of the changes and studies of their effects, 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 the 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 in 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 the chances that the difference would be less than 1.96 times the standard error are about 95 out of 100.

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

Percentage:

  se = square root of (b/N)(p)(100-p)
where p
N
b
=
=
=
the percentage (0 < p < 100),
the population on which the percentage is based, and
the regression parameter, which is based on a generalized variance formula and is associated with the characteristic.

For 2006, 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 variance 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 = square root of (bx)(1-(x/T))
where x
T
b
=
=
=
the number of persons (i.e., dropouts),
population in the category (e.g., Blacks ages 16–24), and
as above.

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3 This age range was chosen in an effort to include as many students in grades 10–12 as possible. Because the rate is based on retrospective data, it is lagged one year, meaning that some 15-year-olds have turned 16 by the time of the interview.
4 Age 16 was chosen as the lower age limit because, in some states, compulsory education is not required after age 16. Age 24 was chosen as the upper limit because it is the age at which free secondary education is no longer available and the age at which the average person who is going to obtain a GED does so.
5 Age 18 was chosen as the lower age limit because most diploma holders earn their diploma by this age. Age 24 was chosen as the upper limit because it is the age at which free secondary education is no longer available and the age at which the average person who is going to obtain a GED does so.
6 For a comparison of estimates from the CPS and the GED Service of the number of 18- through 24-year-olds who have received a GED, see table A-1 in Laird, J., DeBell, M., Kienzl, G., and Chapman, C. (2007). Dropout Rates in the United States: 2005 (NCES 2007-059). U.S. Department of Education. Washington, DC: National Center for Education Statistics.


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