Monthly Labor Review February 2005 63

Respondent Attrition

T

he central problem of longitudinal surveys

is attrition. The National Longitudinal

Survey of Youth in 1979 (NLSY79), which

this issue of the Monthly Labor Review features,

is the gold standard for sample retention against

which longitudinal surveys are usually

measured. However, we cannot understand how

the NLSY79 has done so well without considering

what was done differently in the other cohorts of

the NLS and what we have learned by formal

evaluations of attrition aversion measures that

evolved over a quarter century of field work. The

lessons here are hard-won and, to some,

unconventional.

Background

The NLS began in 1965 at the urging of an Assistant Secretary of Labor, Daniel Patrick Moynihan.

He believed that although the Current Population Survey provided crucial snapshots of the

Nation’s labor force and labor market, the Nation

needed a data source that was more dynamic and

capable of tracking the long-run evolution of careers. The task of starting the study went to

Howard Rosen at the Department of Labor, who

enlisted Herb Parnes from Ohio State University,

to assemble a team, design the surveys, and analyze the data. This team comprised representatives from the Census Bureau, Ohio State University, and the Department of Labor.

The original plan was to follow the cohorts

for 5 years to study some of the pressing questions of the time—the shrinking labor force participation rate of older men, the problem of youth

unemployment and the transition from school to

work, and the growing labor force participation

of women whose children were entering school,

leading to steady growth in the number of working mothers. Childcare was an important issue

along with the problem of how the family would

pay for a college education for the children of the

baby boom.

Over time, the project has expanded. (Table 1

shows the various cohorts of the NLS, their start

and stop dates, sizes, and age ranges covered.)

Because the project began with a 5-year horizon,

neither the Census Bureau, Ohio State, nor the

Department of Labor had a plan for sample retention over the long run; after all, longitudinal surveys were still quite rare. The studies shortly

proved their worth and the project became openended in terms of duration. However, the original

limitations on intended duration led to some problems with attrition that conflicted with a revised

plan to follow the respondents over the balance

of their lives. In particular, the “following-rule”1

that the Census Bureau used specified that when

a respondent missed two consecutive interviews,

the Census Bureau would drop that respondent

from the study.

The following-rule and the original 5-year hoThe problem of respondent attrition:

survey methodology is key

Longitudinal surveys will suffer from attrition

and nothing will change that; however,

years of lessons learned in the field show that

straightforward survey methodology

can minimize the impact of losing respondents

Randall J. Olsen

Randall J. Olsen is

professor of

economics at the

Ohio State University.

E-mail:

olsen@postoffice.chrr.

ohio-state.edu.
64 Monthly Labor Review February 2005

Respondent Attrition

rizon struck with the greatest force on the Young Men’s cohort. In 1981, about two-thirds of the cohort responded to

the survey. Some analysts believed that the rate of attrition

reflected veterans’ refusing to participate in a Government

survey. Although the rate of attrition among black veterans

was a few percentage points higher than that for

nonveterans, for whites, the differential for veterans as a

whole was essentially zero. Within the Young Men’s cohort,

blacks had the highest attrition rates. For whites, attrition in

the Young Men’s cohort was a bit higher than that for two

women’s cohorts, but male respondents have always had

higher attrition than females.

The two-and-out-following-rule that the Census Bureau

employed had serious ramifications, given the attrition pattern for the young men, and high attrition among blacks. By

1981, the Census Bureau had stopped tracking 11 percent of

the young men because they had, at some point, missed two

consecutive interviews. Blacks make up 28 percent of the

young men’s sample, but 57 percent of the cases dropped

because of the following-rule were black. Our current ruleof-thumb is that in the next round, one can obtain an interview on about 25 percent of the respondents who have

missed two interviews in a row. When interviewing began

for the NLSY79, performance specifications did not allow respondents to be dropped simply based on consecutive

missed interviews.

The original design for the surveys alternated in-person

interviews with telephone and mail-out surveys, with the inperson version conducted every 5 years.2

 As a result, the

content of the interview was more comprehensive every 5

Table 1. Survey groups, sample sizes, interview years, and survey status, National Longitudinal Survey, 1966–2004

Age cohort Number Number

 Survey group at first of at last Status

interview surveys interview

Older Men ................... 45–59 4/1/06–3/31/21 5,020 1966/1990 13 12,092 Ended

Mature Women ............ 30–44 4/1/22–3/31/37 5,083 1967/2003 21 2,236 Ended

Young Men .................. 14–24 4/1/41–3/31/52 5,225 1966/1981 12 3,398 Ended

Young Women ............. 14–24 1943–53 5,159 1968/2003 22 2,857 Ended

NLSY79 ........................ 14–21 1957–64 212,686 1979/2004 21 37,724 Continuing

NLSY79 Children ........... birth–14 (4) (5) 1986/2004 10 33,229 Continuing

NLSY79 Young Adults .....

615 and older (4) (5) 1994/2004 634,238 Continuing

NLSY97 ........................ 12–16 1980–84 8,984 1997/2004 7 7,756 Continuing

1 Interviews in 1990 also were conducted with 2,206 widows or other

family members of deceased respondents.

2 After dropping the military (in 1985) and economically disadvantaged

non-black/non-Hispanic oversamples (in 1991), the sample contains 9,964

respondents eligible for interview.

3 The latest sample size available is from the 2002 survey. The 2004

survey is currently being fielded.

4 NLSY79 Children and young adults included by relation to NLSY79

years, with smaller updates in between. The NLS approach to

the Mature Women’s cohort is emblematic of the general approach of the survey. The 1967 interview of the women ages

30–44 focused on the longest held jobs between schooling

and marriage, between marriage and the birth of her first child,

and after the birth of the first child. The survey sought the

most important (that is, longest held) job holdings, probed

for significant periods not working, and ascertained why the

woman did not work. The respondent answered CPS questions about the previous week; these questions accounted

for a significant part of the interview.

This approach to collecting labor force behavior data left

unanswered questions about work history, especially for

women with frequent job transitions and women who missed

the in-person interview. There were modules that collected

retrospective data about fertility and marriage, but in the

1960s, marriages ending in divorce were less frequent, compared with current divorce rates. The NLS did not attempt to

collect an event history on marriage, but nonetheless, the

survey probably collected most of the transitions in marital

status and cohabitation for the Mature Women and Older

Men’s cohorts.

The original cohort data collection effort frequently captured data on respondents’ behavior by asking retrospective

questions, sometimes at wide intervals, to capture particular

data domains. For example, rather than collecting pregnancy

roster data on the Young Women’s cohort as those events

occurred, the NLS would ask about many years’ experience all

at once. As Frank Mott documents, this strategy for data

collection opens the way for more measurement error. 3

females, not birth year. Children are still being born.

5 The size of the NLSY79 child sample depends on the number of children

born to female NLSY79 respondents, attrition over time, and the gradual

aging of the children into the young adult sample. The size of the young

adult sample depends on the number of children who reach age 15 in each

survey year.

6

 In 1998 only, the young adults eligible for interview were limited to

those ages 15 to 20.

Birth year

cohort

Original

sample

Initial year/

latest year
Monthly Labor Review February 2005 65

 With the strategy used then, missing one interview can

leave an important part of the data record distressingly incomplete.

It is in this context that we start this article by focusing on

the historical record of the completion rates for the various

cohorts of the NLS and how the strategy for both data collection and the rules for continuing to follow nonrespondents

generate startling impacts on the completeness of the data

coming out of a longitudinal study. This article continues by

describing some of the fielding techniques the NLS program

has employed to offset the secular trend toward lower completion rates.

The historical record

The remainder of this article describes the two original

women’s cohorts: the NLSY79 and the NLSY97. The two original men’s cohorts were cancelled in the early 1980s.4

 In 1981,

the Census Bureau completed interviews of 65 percent of the

original respondents for the Young Men and 52.5 percent of

the Mature Men. However, corrected for mortality, the numbers are higher, with 66.8 percent completed of the respondents still alive for the Young Men and 74.8 percent of the

Mature Men. After 15 years, the completion rate for the Mature Women was 69.7 percent (73.5 percent of those still alive),

and for the Young Women it was 68.8 percent (69.4 percent of

those still alive). As mentioned earlier, the lower completion

rate for the Young Men reflects a following-rule that dropped

blacks at an unusually high rate.

The Census Bureau experience with the original cohorts

was more favorable than its recent experience with respondents from the Survey of Program Dynamics (SPD). That survey continues the 1992–93 Survey of Income and Program

Participation (SIPP) panel. By the end of the SIPP phase for

the SPD respondents (the SIPP phase contained nine waves

each 4 months apart), the completion rate was about 73.4

percent. The 1997 wave of the SPD completed 58.7 percent of

the SIPP respondents, and by 2002, the completion rate stood

at 53 percent of the 1992–93 SIPP respondents. The 10-year

retention rate for the SIPP/SPD panel is below the 15-year

retention rate for the original cohorts, whether or not one

corrects the latter retention rates for mortality. A more striking contrast is the experience with the NLSY79, for which the

National Opinion Research Center (NORC) does the data collection. The 15-year retention rate from 1979 to 1994 was 89.2

percent—almost 20 percentage points higher than the rate

for the original cohorts. The disparity of experience with

retention in longitudinal studies grows when we compare the

NORC experience with the NLSY97 to their experience with the

NLSY79. After seven rounds, NLSY97 retains 86.4 percent of

the respondents, which is below the NORC experience in the

NLSY79 after more than 19 years. Even if we examine the

records of the Census Bureau and NORC separately, we see

marked variation in outcomes. The reason for this disparity is

complex.

Bounded interview event histories

The most important feature that distinguishes the NLSY79

(and NLSY97) from the initial design of the original cohorts of

the NLS is the use of event histories in the NLSY79 and

NLSY97. The article by James Walker in this issue addresses

this feature in more detail, but when the case for event histories in the NLSY79 was made by Burton Singer, he had in mind

their analytic usefulness and not their effect on attrition. (See

accompanying articles in this issue.) As it turns out, event

histories in longitudinal surveys force us to rethink our views

on attrition.

As implemented in the NLSY79, event histories carried forward respondents’ answers to questions from the previous

interviews in some domain. For example, if the respondent

was interviewed on July 21, 1987, and he was married, we

would ask, “According to our records, when we last interviewed you on July 21, 1987, you were married. Is that correct?” If the respondent agrees, he would be asked whether

his marital status has changed since that date, and if so,

when that happened, what the change was, and the characteristics of that transition, such as the demographics of the

new spouse, and so forth.5 If the respondent disagrees with

the data carried forward in our records, the interviewer obtains the corrected data and then carries the event history

collection forward from the point of correction.6 This approach allows one to deal with the “seam problem,” namely

how to deal with recollections of the same event whose timing differs across survey waves. Indeed, when the NLSY79

switched to computer-assisted interviewing and, at the same

time, to collecting a true event history for education, the incidence of seam problems declined dramatically.

Perhaps more importantly, the use of bounded interview

event histories makes the data collection protocol less dependent on the interview date. If a respondent misses an

interview, at the next round he is asked to pick up the collection of the event history on, say, marital status at the point he

left off on the most recent completed interview. We recover

event history data from a respondent whenever he or she

returns to the survey. This approach generates a substantially more complete data history for respondents than suggested by a simple examination of completion rates.

Chart 1 illustrates the effect of returning to respondents.

The lower line is the round-by-round completion rate for the

NLSY79 from the 1st through 20th rounds. The higher line

shows the fraction of the data for the year preceding each of

the 20 rounds that we recovered either from an interview in

that or a subsequent round. Because we fill in missing data
66 Monthly Labor Review February 2005

Respondent Attrition

for the event histories whenever we interview the respondent, analysts have well in excess of 90 percent of the data

for 20 years after the initial interview. Bounded interviewing

requires a sophisticated instrument, adds to interview length,

and works best with salient events. With long retrospectives,

accuracy may suffer, but missing data are the worst data. In

the NLSY79 and NLSY97, we employ event histories for employment, marriage and cohabitation, fertility, training, education, and program recipiency. These histories are the core

of the NLS.

Using bounded interviewing event histories generates a

more complete data record, especially when combined with a

field strategy that emphasizes returning to past

nonrespondents. Charts 2 and 3 illustrate how the decision

on which respondents to contact in a longitudinal survey is

crucial to generating a complete data record.

 In the Young Women’s and Mature Women’s cohorts, the

Census Bureau originally adopted the strategy that it would

not return to any respondent who refused two straight interviews. In the mid-1980’s, the Census Bureau changed that

strategy. Starting in 1985, the Census Bureau returned to

past nonrespondents to the Young Women’s survey, and in

1986, the Census Bureau no longer dropped respondents

missing two straight interviews, but did not return to past

nonrespondents.

Chart 2 shows that the rate of attrition slowed after the

Census Bureau no longer dropped nonrespondents after they

missed two straight interviews, effective in 1985. The event

history completion rate naturally shows less data loss once

the Census Bureau changed their following-rules. Chart 3

illustrates the impact of the Census Bureau’s decision in 1986

to return to some (but not all) of the Young Women who had

been dropped from the survey roster after two straight noninterviews. The completion rate jumped up when the Census

Bureau started the new following-rules, and in subsequent

rounds, the completion rate dropped more slowly. The impact

on the event history completion rate of former nonrespondents,

(especially in contrast to chart 2 for the Mature Women), provides stark evidence that an aggressive following-rule plus

bounded interviewing event histories are valuable data-collection strategies for the NLS. Next, we turn to encouraging the

respondents to give us more interviews.

Encouraging respondent cooperation

The NLS has a life-cycle perspective; it tries to follow respondents from their first interview to the end of their life. Sometimes funding constraints limit how long it can follow a cohort, but the project tries to keep its focus on how lives of

individuals evolve in their entirety. This scientific agenda

requires patience and a focus on long-term cooperation. The

other long-term survey best known among social scientists

is the Panel Study of Income Dynamics (PSID). That study

focuses on the household rather than on the individual, so if

we lose the cooperation of one reference person for the

household, we seek another informant for that household. In

Chart 1. Comparison of data recovery rates from ordinary round-by-round interviews and event 

 history with bounded interviewing, NLSY79 youths, ages 14–21 in 1979

 Recovery rate Recovery rate

0 5 10 15 20 25 30 35 40

50

60

70

80

90

100

50

60

70

80

90

100

Years from first interview

Ordinary completion rate

Completion rate from event history

NOTE: Year "0" is 1979.

SOURCE: Author's calculations. 
Monthly Labor Review February 2005 67

Click here to type page title

Recovery rate Recovery rate

Years from first interview

0 5 10 15 20 25 30 35 40

50

60

70

80

90

100

50

60

70

80

90

100

Single-round interview

Bounded interview

Chart 2. Comparison of data recovery rates from single-round inteviewing and event history 

 with bounded interviewing from women ages 14–24 in 1967

NOTE: Year "0" is 1979.

SOURCE: Author's calculations. 

Recovery rate Recovery rate

Years from first interview

0

50

60

70

80

90

100

50

60

70

80

90

100

Single-round interview

Bounded interview

5 10 15 20 25 30 35 40

Chart 3. Comparison of data recovery rates between single-round inteviewing and event history 

 bounded interviewing, women ages 30–44 in 1967

NOTE: Year "0" is 1979.

SOURCE: Author's calculations. 
68 Monthly Labor Review February 2005

Respondent Attrition

the case of the NLS, we only use proxy respondents for ill

individuals or in other unusual cases. This puts a premium

on retaining the good will of respondents. We seek the goodwill of the respondents in three major ways: informing the

respondent about survey objectives and findings, using incentive payments, and employing the mode of interview that

the respondent prefers.

Fundamentally, to gain respondent cooperation, field staff

must stress that the study is important, if not for the respondent, then for society at large. The questions have to be valid

and must relate to the objectives of the study that form the

basis for its societal usefulness. For the doubting respondent, the study must provide evidence that it is substantiated by findings, recommendations, or a body of research

consistent with the message that it is important. Interviewers play a pivotal role in the “selling of the survey.” Thus, a

less appreciated corollary of convincing respondents that

the study is important is that the interviewers must be convinced the study is important. What good is a salesperson

who does not believe in the product?

The NLS program mails out informative brochures to respondents and provides the interviewers with packets of

materials that provide support for the central thesis that the

study has societal importance. It also provides items to rebut common objections to cooperating with the survey. However, the most important tool we have is the enthusiasm and

commitment of the interviewers. We communicate this in two

forms—first by engaging and “selling” the interviewers when

they attend training, and second through their interaction

with the field managers who have day-to-day responsibility

for overseeing the field work. Tepid and boring training sessions for interviewers are not only ineffective venues for

learning, but they communicate a subliminal message to interviewers that the larger survey is equally boring and, hence,

unimportant.

Although we attempt to communicate the scientific importance and social utility of the survey, some respondents remain unconvinced. Respondents are not monolithic. About

half the respondents are extremely cooperative and easy to

work with. As of 2002, almost exactly 60 percent of the respondents in continuing sample types 7

 had completed every

interview. There is also a core group of very disaffected

respondents for whom we have little hope they will complete

the survey, although from time to time a few rejoin. For these

hard-core refusers there is not much that will make a difference in their cooperativeness, at least nothing we have been

able to identify and use. However, for a sizeable minority of

the sample, respondent incentives, either money or in-kind,

can play a useful role in securing cooperation with the survey. Small gifts that are tailored explicitly to the interests and

situation of the respondent can be very effective—they say

in a tangible way that we care about the respondent and pay

attention. Although incentive payments likely influenced

some of the respondents who have remained with the survey

throughout, incentives appear to work on a minority of respondents—a fact that needs to be integrated with any plan

to use incentives in longitudinal surveys.

 In 2000, we conducted an experiment, with randomization

of subject and treatment, investigating the effects of a $40

versus $80 incentive. With the two incentive amounts, we

computed how much additional money we spent to obtain an

additional interview. On the one hand, when additional incentives were offered to respondents not interviewed in 1998

(the previous round—the NLSY79 is now administered every

2 years), we made $167 in additional incentive payments, on

average, for every additional interview when increasing the

payment from $40 to $80. On the other hand, for respondents

who had cooperated in 1998 we paid an additional $264 for

each additional interview. This experiment was conducted

when we had encountered strong resistance and sharply

higher field costs when using an across-the-board $20 incentive. Had the experiment been mounted at the beginning of

the field period, the higher payments would have been even

more cost-ineffective.

Across-the-board incentive payments increase response

rates at a substantial monetary cost. However, one unexpected result of the experiment in 2000 was a reduction in

field costs that coincided with the higher incentive payments—field costs fell in a manner we had not seen in previous rounds. The savings in field costs very nearly offset the

higher respondent fee costs. Survey organizations should

consider the effects of incentive fees, not only on respondent cooperation, but also on the overall cost-effectiveness

of a survey campaign.

The most frequent objection to differential fees cites equity issues. This objection, together with the surprising finding in the 2000 round that higher fees reduced field costs, led

us to experiment in 2002 with a strategy aimed at using higher

incentives with cooperative respondents. For this experiment, called the “Early Bird,” we mailed a flyer to respondents offering a higher fee if they called in to make an appointment for an interview. Because interviewers expend

substantial time locating, contacting, and making an appointment with respondents, the “Early Bird” offer saves money

despite the higher respondent fee involved. Once the conventional field period begins, the offered incentive payment

reverts to the normal level.8 Respondents requesting a higher

fee are encouraged to participate in the Early Bird program—

interviewers redirect requests for a higher payment toward

enrolling the respondent in a mutually advantageous compact exchanging more cooperation for a higher fee.

 Although incentive payments encourage some respondents to participate, these payments cannot, within a reasonable range, convert all or even nearly all nonrespondents.
Monthly Labor Review February 2005 69

Fees work for some and fail for others. In addition, for some

groups of respondents, such fees can be very expensive in

terms of how many cases the extra money spent produces. In

short, respondent reactions to incentive fees are remarkably

heterogeneous.9

Heterogeneity also rules when it comes to the interview

mode that respondents prefer. The survey choices available

to respondents are via telephone, in-person interview, or, to a

lesser degree, Webpage. However, the NLS surveys are too

complex to encourage most respondents to take a mail survey or a Web survey—most interviewers require about 2 days

of training on the survey before they are ready to administer

it. Some respondents, having done the survey 20 times before, are more “experienced” with the survey than new interviewers, but there are sections of the interview where interviewer training plays an important role. For this reason, the

NLS program does not routinely offer respondents the choice

to do the interview over the Web, although we could offer

this option.10 When it comes to telephone versus in-person

interviews, some respondents insist on a telephone interview and others insist on in-person interviews. The initial

approach to each respondent is usually over the telephone,

except in unusual circumstances. At that point, respondents

for the NLSY79 can choose how they want to do the interview. With the NLSY97, the survey contains a substantial

self-administered section containing sensitive questions, and

interviewers emphasize in-person interviews. The latter constraint generates comments from the field staff indicating the

emphasis on in-person interviewing tends to increase costs;

however, if the choice is between a telephone interview and

no interview, the field staff always goes for the interview.

The essential point is that respondents vary in their preferences, and insisting on either telephone or in-person interviews carries substantial risk of alienating respondents.

 In this same vein, organizations conducting longitudinal

surveys often question whether having the same interviewer

do a case year after year encourages response.11 Knowing

whether continuity in the assigned interviewer encourages

response would allow a field organization to assign cases

more strategically and to make a more intelligent trade-off

between reducing travel costs and reducing assignment turnover. Our ability to infer the relationship between attrition

and interviewer turnover is reduced by the fact that field

operations rarely employ random assignment of interviewer

and respondent to a dyad. If one interviewer has trouble with

a case, we assign a new interviewer and hope for better results. In short, random influences that make a respondent

less likely to do an interview can also lead to a change in the

assigned interviewer. Indeed, a case may have several interviewers assigned to it over the course of the field period.

Because of these problems, we look at respondent attrition

using variables that summarize his or her past tendency to do

the survey, his or her attitude at the most recently completed

interview, and respondent age. To capture the effect of interviewer continuity, we use two additional variables, whether

the interviewer doing the respondent’s most recent interview

is still on staff and, if so, how many times that interviewer had

interviewed the respondent. These two variables only measure the ability of the field staff to exploit interviewer continuity in the current round, not whether interviewer continuity held for the current round.

The results, in table 2, using 202,245 observations from

rounds 2 through 20 of the NLSY79, suggest that interviewer

continuity is not a major factor. There is a net advantage to

interviewer continuity after the respondent has been interviewed twice by the same interviewer, and after that, having

the same interviewer decreases attrition by about 0.7 percent

for each additional round. If an interviewer had interviewed

the respondent for the previous round, having that interviewer on staff again generates no positive effect (for the

Table 2. Probability of respondent cooperating with current NLSY79 round

 Variable Coefficient Effect1 (dP/dX) Standard error t-ratio

 Sample size, N=202,245

Intercept ................................................................ –2.4002 ... 0.2219 10.82

Respondent did round before? .................................. 2.8604 0.212 .0296 96.64

Previous interviewer on staff? ................................... –.0914 –.007 .0289 3.16

Previous interview by phone? ................................... –.5067 –.037 .0256 19.79

Number of interviews done by previous

 field interviewer, previous interviewer on staff ........ .0881 .007 .0089 9.90

Percent of previous interviews done .......................... 3.8157 .282 .0721 52.92

Respondent hostile at previous interview? .................. –1.5691 –.116 .0917 17.11

Respondent impatient, restless? ............................... –.9364 –.069 .0421 22.24

Respondent cooperative, not interested ..................... –.5107 –.038 .0249 2.51

Age R .................................................................... .0142 .000 .0141 1.01

Age R squared ........................................................ –.0011 .000 .0002 5.50

1

 The effect on the probability of an interview on a unit of change in the explanatory variable.
70 Monthly Labor Review February 2005

Respondent Attrition

NLSY79, if the same interviewer is available, she will most

likely have any of her previous cases that are in the same

geographic area).

Also in table 2, the estimated model is a logit. The third

column gives the effect on the probability of an interview of

a unit change in the explanatory variable. The standard error

is for the coefficient. Results show that it is, by far, more

important to keep the respondent interested in the project

and happy with how they are treated than to keep the same

interviewer. Of course, interviewer continuity may make it

easier for the field staff to remember how best to deal with a

particular respondent.

LONGITUDINAL SURVEYSWILL SUFFER from attrition and nothing

will change that. However, certain survey methodologies can

minimize the impact of attrition. First, if consistent with its

objectives, the survey should utilize event histories to recover data not collected when a respondent misses a round.

Notes

1

 This is the rule determining to which respondents interviewers

would return in the event the respondent did not complete one or

more interviews.

2

 Census interviewed the young men and young women in person

for several consecutive years and then reverted to the interview

pattern for the two older cohorts—personal, skip a year, telephone,

skip a year, telephone, personal. In the late 1980s the women’s

interviews were done in person, although many cases were done over

the phone when circumstances dictated.

3

 See Frank Mott, “Looking Backward: Post Hoc Reflections on

Longitudinal Surveys,” in Erin Phelps, Frank Furstenberg, and Anne

Colby, eds., Looking at Lives: American Longitudinal Studies of the

Twentieth Century (New York, Russel Sage, 2002).

4

 The two original men’s cohorts—NLSY79 and NLSY97 were cancelled

in the early 1980s.

5

 With the rise of nonmarital unions, event histories on marriage

and cohabitation have become more complex. The approach of asking

the retrospective question with explicit reference to the respondent’s

previous answers is referred to as “bounded interviewing.”

Second, the following-rules must emphasize persistence. If a

respondent refuses a round, return in the next round. When

respondents miss a round, in about half the cases they will

grant an interview for the next round. If they miss two straight

interviews, the probability of success drops to about 25 percent, but certainly not to zero. Third, targeted incentive payments should be used because they are cost effective ways

of holding attrition in check. Fourth, allow respondents to

choose the interview mode. Just as differences in respondents

make incentives effective only for some respondents, differences among respondents make it important to acquiesce to

their preferences over interview mode (phone versus personal

or even Web). Finally, longitudinal surveys must be “sold.”

They must be sold to the interviewers who face the job of

convincing the respondent that the survey is important, and

they must be sold to the respondent who, in the majority of

cases, will offer their cooperation so long as the study engages their attention and they are confident that they are

providing their time for a worthy endeavor. 

6

 The discrepancy is handled at Ohio State. This style of data

collection generates fewer “seam problems” than histories that are

not collected using bounded interviewing. Our current practice is to

accept the date given initially and place the “seam” on the day after

the date of interview.

7

 The low-income, non-black, non-Hispanic oversample was nearly

eliminated in 1993 and most of the military oversamples were dropped

earlier.

8

 Currently the normal incentive is $40.

9

 In the past 15 years, we have also experimented with monetary

incentives to interviewers. Unfortunately, those experiments failed.

At best, they simply shifted the timing of when cases were completed.

10 Our CAPI system is based entirely on Web browsers. Some interviews

done over the phone utilize the Web to present the interview to the

interviewer, so offering a Web interview to respondents is a minor step.

11 The other side of repeated contact is that the respondent may be

more likely to give normative responses to an interviewer once they

have established rapport.