Center for Demography and Ecology

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1 Center for Demography and Ecology University of Wisconsin-Madison Keeping Track of Panel Members in Longitudinal Research: The Experience of the National Survey of Families and Households Vaughn R. A. Call NSFH Working Paper No. 38

2 KEEPING TRACK OF PANEL MEMBERS IN LONGITUDINAL RESEARCH: THE EXPERIENCE OF THE NATIONAL SURVEY OF FAMILIES AND HOUSEHOLDS Vaughn R.A. Call NSFH Project Associate Center for Demography & Ecology University of Wisconsin - Madison 4412 Social Science Building Madison, Wisconsin The National Survey of Families and Households was funded by grant HD from the Center for Population Research of the National Institute of Child Health and Human Development. Analyses were performed using Center for Demography and Ecology Facilities provided under grant HD This report updates the information provided in the 1989 report on tracking progress and procedures. KEEPING TRACK OF PANEL MEMBERS IN LONGITUDINAL RESEARCH: THE EXPERIENCE OF THE NATIONAL SURVEY OF FAMILIES AND HOUSEHOLDS

3 The design of the National Survey of Families and Households includes a five-year longitudinal follow-up to permit the assessment of change in American family life. One of the biggest potential threats to this panel design is panel attrition. By 1992, about half of the original NSFH sample will have moved from their 1987 address. The goal of the NSFH tracking effort is to reduce panel attrition by obtaining as many of these address changes as possible through use of the National Change of Address (NCOA) services of the U.S. Postal Service, as well as encouraging the respondent to inform us about moves. We utilize this "soft" tracking approach in order to reduce costs for the subsequent major tracking effort and to avoid antagonizing respondents with numerous direct contacts prior to the wave II survey. The importance of the respondent to the success of the survey and the policy and scientific importance of the survey are the major messages conveyed to the respondent in all correspondence. We emphasize the importance of the respondent by personalizing correspondence as much as possible. TRACKING PROCEDURES The tracking design for the NSFH interim years involves a series of letters or reports mailed annually to each respondent. All letters have "Forwarding and Address Correction Requested" printed on the outer envelope to request Post Office address correction services and contain a request in the letter or brochure for the respondent to notify us of any moves. All envelopes are number 10 bond envelopes attached to a continuous-form, track-feed carrier that permitted us to easily type the name and address of the respondent directly on the envelope. We further avoid the appearance of a bulk mailing by including commemorative postage on each envelope. The 1988 letter to the respondent was personalized with the respondent's name, address, and salutation. In 1989, we sent a brochure enclosed in a personalized #10 envelope, but no letter in order to reduce costs. Given a substantial drop in address corrections received from respondents in 1989, we incorporated a letter format into the 1990 brochure to reinforce the request for address changes. Address corrections from respondents increased. We will utilize the 1990 letter/brochure format in our 1991 mailings. Copies of the letter, brochures, and envelope are included in the appendix. Each year we mail respondents with current addresses a letter that arrives the calendar month prior to the original interview month. Since the Post Office provides address correction services for a period of one year (and holds the address for an additional six months), the eleven month procedure minimizes potential loss of available address corrections from the Post Office. In order to

4 avoid overlapping mail preparation tasks in February-May, we combined the few interviews completed in the first half of 1988 into a large January mailing. These respondents received their initial letter from six to eleven months after their interview. MASTER ADDRESS FILE During the early part of 1988, we used names and addresses provided by Temple from their check-in file as the basis for our Master Address File (see appendix). Temple staff had not checked these names and addresses for spelling errors and accuracy. Moreover, the third tape from Temple contained updates and changes in names, addresses, and comments that differed from the initial tape Temple forwarded to us. The unverified names and addresses from the third tape were used without editing so that we could maintain our eleven month mailing schedule. We used information obtained from mail returned as undeliverable, the post office address correction forms, and letters from respondents to update the respondent name, address, and status code data in the Master Address File. When a letter or form is returned, the information is entered via special software that prompts for information to be input and restricts the types of changes that can be made to the Master Address File given prior information about each case. SPECIAL EDIT OF MASTER ADDRESS FILE Upon receipt of the original interview schedules, cover sheets, and screener forms from Temple, we initiated an intensive verification process during the latter part of All information about each respondent was assembled (cover sheet, screener form, returned 1988 envelope - if any, address correction forms, respondent letters, and comments from the first and third Temple check-in file tapes). We compared this information to verify the name and address of each respondent in our Master Address File. We developed an interactive editing program to make all editing changes to the Master Address File. When a change is made in a particular record, an historical log of all "old" information is kept in a History File. The History File contains a copy of the entire Master Address record for a case as it was before the change was made to the case. If during the verification process we discovered errors of omission or commission that could have affected the delivery of a 1988 letter, we marked the case and a new letter was sent in 1989 using the updated information. We include a flowchart of this entire process in the Appendix.

5 RESPONSES Table 1 provides the monthly mailing results for 1988 through Readers will note a number of anomalies. First, number of letters mailed for particular groups in 1989 sometimes exceeds the 1988 mailing for that group. Corrections made in the month of interview moved some respondents to a different mailing group. Second, the 1989 mailings are greater than expected given the number of 1988 undeliverable letters. Thirty-one percent of the 1988 letters returned as undeliverable were marked "insufficient address". These and any other letters with questionable addresses were changed and the respondent was sent a new letter in Third, you will note that the frequencies from Table 1 do not exactly match the frequencies in subsequent tables, particularly with respect to Post Office address corrections. Table 1 is an unedited check-in count that did not remove multiple returns and invalid ID numbers (cases subsequently removed from the data file because of termination of the interview). Multiple returns occur when a respondent moves more than once in a year and files address correction forms with the post office. At the end of 1988, there were current or likely addresses for 12,469 of the original respondents (95.8%). At the end of 1989 there were 11,537 current addresses (88.6%). By January, 1991, we had current addresses for 10,892 panel members (83.7%). These may be high estimates because the post office loses some mail and other mail may be delivered to the listed address but not the respondent. We assume that the letter reached the respondent when, in fact, the current occupant may have thrown our letter away or forwarded it to the respondent. The undeliverable rate was 6.4 percent in In 1989, the rate fell to 5.1 percent. The rate dropped slightly in 1990 (4.9%). Extrapolating the "worst case" undeliverable rate (6.4%) over the five year period to 1992 results in a loss of addresses for about 27 percent of the 13,017 respondents. This may be a liberal estimate because we are dealing with a fixed group of people who may tend to move less as they age and the second mailing culled out most remaining bad addresses. Nonetheless, it would not be unreasonable to plan for intensive tracking in 1992 for 25 to 30 percent of the original respondents TABLE 1. Response Patterns to the Tracking Letters. ))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))) PERCENT PERCENT WITH

6 NUMBER MAILED UNDELIVERABLE ADDRESS CORRECTION Mar % 8.0% 5.6% 9.5% 5.4% 10.2% Mar Apr May June July Aug Sep Oct Nov Dec Jan ,057 12,469 11, % 6.4% 5.3% 9.8% 8.3% 7.5% 100%* 96%** 89% ))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))) * The initial mailings contained 40 names that were later dropped from the sample. ** Corrections to name and address lists occurred during the 1988 mailings. About 250 previously undeliverable letters were r ed in 1989 to the corrected addresses POST OFFICE ADDRESS CORRECTION Of the 1092 respondents for whom at least one address correction was received in 1988, 82 percent of those corrections came just from the Post Office (See Table 2). An additional 10 percent had both corrections from the Post Office and the respondent. Eight percent, however, came only from the respondent. This eight percent may represent the failure of Post Office personnel to return a correctly filed address correction. Conversely, it may represent the willingness of respondents to provide us an address correction that they did not provide the post office. Receipt of address corrections varied greatly by year. In 1989, over 89 percent of the 918 address corrections came just from the post office. Only three percent had corrections from both the post office and the respondent, and seven percent came just from the respondent. The percentage of address corrections received from just the post office fell to 80 percent in Seven percent came from both and over 13 percent came from the respondent only. The 1990 figures might suggest a degradation in the Post Office's

7 address correction service Table 2. Response Code Results by Year ))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))) RESPONSE CODE N % N % N % Insufficient Address % No forwarding Address Addressee unknown No Mail box Other undeliverable Address correction from Post Office Address correction from Respondent Address correction from P.O. and R Letter Presumed Delivered Letter Not Sent % % % CURRENT STATUS OF MASTER ADDRESS FILE We ended three years of tracking with current addresses for 83.7 percent of the file. We have lost contact with 16 percent of the respondents (see Table 3). This does not mean that 16 percent of the file will be difficult to find. In the following section, we find that most of those who moved without leaving a forwarding address did provide us the name of at least one friend or relative to contact. There have been 29 deaths reported to us. These reports were mostly a note saying "deceased" written on the letter and returned to us. In one instance we received death certificates from the executor of the estate. Our procedures have been very successful in keeping refusals to a minimum. Only three people have written and asked to have their name removed from the study.

8 Table 3. End of Year Address Status Codes by Year ))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))) N % N % N % Not Current, but last known address Current New Address (change of Address) Respondent Refusal (letter from R.) Respondent Deceased (note from P.O.) Do Not Contact Unclaimed letter Original Address (presume letter was delivered) TOTALS % % % NUMBER OF CONTACTS As part of our editing process, we added the number of references listed on page 158 of the Main Interview to the Master Address File. If a listed reference lived outside the U.S. or did not have a complete address, these references were not counted (see Table 4). We did not count references at the same address as the respondent unless they had different phone numbers Table 4. Reason Listed Reference Was Not 5 5 7Counted as a Contact 5 K)))))))))))))))))))))))))))))))))))))))))))))))))))M 5 N Reason not counted All references outside U.S One or two references outside U.S One reference lives with R 5

9 5 25 Two references live with R 5 5 Number of reported references: ( 9.7%) No references ( 19.3%) One reference ( 24.4%) Two references ( 46.6%) Three references (100.0%) Of the 1261 respondents with no references, 39 percent overtly refused to provide references. Of these, 440 stated that they refused to give references. Another 28 refused but stated that they were not moving anywhere or would "either be dead or still living here." An additional 24 told the interviewer that they could not think of anyone. The majority of the 1261 respondents did not have anything marked on page 158. We can not tell if these respondents refused to provide references or if the interviewer failed to ask for the references. NUMBER OF AVAILABLE TELEPHONE NUMBERS Approximately 93 percent of households in the United States have telephones. Recent estimates by Survey Sampling Inc. suggest that 31 percent of all phone numbers are unlisted. Ninety percent of our respondents (11,738) provided a telephone number to the interviewer. This suggests that almost all the NSFH respondents who had a phone complied with our request for their telephone number and a third of these numbers may have been unlisted numbers. Most of the numbers were the respondents' residence number. A few telephone numbers belong to someone else (see Table 5) Table 5. Comments on Phone Numbers 5 K)))))))))))))))))))))))))))))))))))))))))))))))))))M 5 N Comment 5 4 belong to a relative 5

10 5 16 belong to a friend are work numbers were obtained from directory assistance were disconnected when Temple tried 5 5 contacting them in 1987/ In 1989, we provided an address correction form in the brochure for respondents to mail to us. We included a request for new phone numbers in this form. Only five respondents who mailed in this form did not include a phone number. Respondents are quite willing to provide us phone numbers on the form -- apparently even unlisted numbers. Our efforts to reinforce the importance and legitimacy of the survey appear to be having the desired effect. POTENTIAL TRACKING DIFFICULTY The lack of a telephone makes respondents difficult to locate. The problem is further compounded when there are no references listed. This often occurs because respondents refuse to give any information. There are 256 respondents who refused to give any phone or reference information (2% of all R's). Eighty percent of respondents without a listed reference did provide a telephone number. As expected, most respondents who provide three references also provided a telephone number Table 6. Number of References and the Availability 5 5 of a Phone Number 5 K))))))))))))))))))))))))))))))))))))))))))))))))))))))))))M 5 TELEPHONE NUMBER 5 5 AVAILABLE 5 5 NUMBER OF NO YES 5 5 REFERENCES 5 5 None 20% 80% 100% (1261) 5 5 One (2510) 5 5 Two (3179) 5 5 Three (6067) Of respondents without a current address at the end of 1990 (N=2125), 21.6 percent did not report a phone number during the

11 original interview. This precludes an easy search via telephone for within area moves for respondents who kept their same telephone number. The worst group is those whose mail came back undeliverable because addressee was unknown. Twenty-three percent did not provide a telephone number. Parenthetically I note that many of the addressee unknowns lived in a trailer court when first contacted. In contrast, about 98 percent of respondents who sent us their address corrections provided a telephone number in The 1990 Address Status shows very little difference in the number of references provided (Table 7). There is a slight tendency for respondents who move without leaving a forwarding address to not provide references or to only provide one reference. There are 211 respondents who are currently "lost" with no references to contact. These percentages have remained almost invariant since the 1988 mailing. The percentage of respondents who are "lost" and did not list any contacts dropped just over a percentage point during the three year period. This suggests that 10 percent or less of the original NSFH respondents will be difficult to locate Table Address Status and Number of Contacts 5 5 Provided in K))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))M 5 NUMBER OF CONTACTS PROVIDED 5 5 ADDRESS 5 5 STATUS None One Two Three Total N 5 5 Not current 10% 23% 25% 42% 100% Moved to New 5 5 Address At Address GEOGRAPHIC DISPERSION OF PANEL MEMBER Another indicator of potential tracking difficulty that could effect panel attrition is the amount of geographic dispersion by panel members.

12 We took the postal zip codes from respondents' 1987 addresses and grouped them by Temple's Primary Sampling Units (PSU). The zip codes of panel members within the original PSU provides a rough geographic criterion from which to assess dispersion. For PSU's with unique zip codes we took the first three digits of the zip code to establish the base delivery area and geographic boundaries of the PSU. Forty-three percent of these PSU's had overlapping postal Zip codes. For these nonunique zip codes, we aggregated the 1987 zip codes and determined from maps the probable allocation of zip codes between PSUs. These procedures established "geographic boundaries" that were largely city based. While we have no way to determine the actual postal delivery areas within the original PSU's, our procedures provide a reasonable approximation to original PSU boundaries. A respondent's move in or out of PSU areas was determined by a comparison of the current 5-digit zip against the list of zip codes assigned to PSUs. By the end of 1990, 16 percent of the original respondent addresses were not current. We lost mail contact with about 5 to 6 percent of our respondents each year since During the same time period, about 17% of our respondents moved and left a forwarding address. Most of these either moved to another sample city (PSU area) or moved within their original zip code TABLE 8. Geographic Dispersion of NSFH Panel Members 5 K))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))M Status N PERCENT 5 5 Moved in 1987 outside PSU % 5 5 Moved in 1988 outside PSU Moved in 1989 outside PSU Moved in 1990 outside PSU Respondent moved within or into 5 5 PSU prior to 1990, address current Moved in 1990 within PSU Respondent still in original home (includes 45 people who are deceased, 5 5 have no mail boxes or requested 5 5 no contact) 5 5 Respondent moved in 1987, no address Letter was undeliverable Letter was undeliverable Letter was undeliverable

13 5 TOTAL % Ninety-four percent of panel members with current addresses are still living in a sampled area (PSU area) after 3 years. About 80 percent of all respondents (those with and without current addresses) continue to live in within original PSU boundaries. The percentage in sampled PSU's could be as high as 93 or 94 percent if the undeliverable movers follow the same pattern as the deliverable movers. The high percentage of respondents living within original PSU boundaries suggests that a face-to-face follow-up interview is feasible. APPENDICES Flowchart of Tracking Procedures Master Address File Codebook Tracking Information Codebook Examples of Correspondence Mailed to Respondents 1988 Letter 1989 Brochure 1990 Brochure 1991 Brochure Envelope used in Mailings

14 NSFH TRACKING PROCESS Names and Addresses 5 5 from Temple 1987/ Check-in File L * /89 First Mailing Post Office Returns 5 5 to Respondents K)))))) 5 and Address 5 5 (personalized) Corrections )))))))))))))))))))))), 5 Master Address File 5 * HISTORY FILE * 5 UPDATE 5@@@@@@@ * (old information) * 5 (status, new addresses) 5.)))))))))))))))))))))) L * )))))))))))))))))))))), 5 Master Address File 5 * HISTORY FILE * /89 TOTAL EDIT 5@@@@@@@ * (old information) * 5 (Verified names and 5.))))))))))))))))))))))- 5 addresses) L * "current" and corrected insufficient address cases * * /90 Second Mailing Post Office Returns 5 5 Mailing to Respondents K))))))) 5 and Address 5 5 (Brochure) Corrections )))))))))))))))))))))), 5 Master Address File 5 * HISTORY FILE * 5 UPDATE 5@@@@@@@ * (old information) * 5 (status, new addresses 5.)))))))))))))))))))))) )))))))))))))))))))))), * Subsequent Mailings * * (1990, 1991) * """"""""""""""""""""""""

15 MASTER ADDRESS FILE NATIONAL SURVEY OF FAMILIES AND HOUSEHOLDS Columns Variable Description 1-5 ID (Numeric) 6-65 Full Name (Alpha) Street and Apt# (Alpha) City, State, Zip (Alpha) Salutation (Alpha) Date Any (Last) Change (Numeric) STATUS CODE (Valid address code) 00 = Not Current, but last known address 01 = Current New Address 02 = Respondent Refusal (letter from respondent) 03 = Respondent Deceased (either letter or note from postal worker) 04 = Do Not Contact (request for no contact) 05 = Unclaimed letter 06 = Undeliverable, but none of above 99 = Current Original Address Response code Response code Response code Response code Response code OLD CHECK CODE 01 = Insufficient Address 02 = No forwarding Address 03 = Addressee unknown 04 = No Mail box 05 = Other undeliverable (see status code) 06 = Address correction received from Post Office 07 = Address correction received from Respondent 08 = Combined Responses from P.O. and Respondent 09 = None of above (Freq=0 on 8/10/89) 99 = Letter delivered, no changes or replies 00 = No name errors, No address errors 01 = Name errors, No address errors 02 = Check name, No address errors 05 = No name errors, Address errors 06 = Name errors, Address errors 07 = Check name, Address errors 09 = Name/Address not checked Old GROUP (Interview Month/Year)

16 Old Date New Date New Group HISTORY CHECK CODES = Checked, Not changed 1 = Checked, Changed 9 = Not checked yet HISTORY CHECK CODES HISTORY CHECK CODES HISTORY CHECK CODES HISTORY CHECK CODES Number of Contacts listed on Tracking Form 0 = none 1-7 = one to seven contacts 8 = 8 or more contacts 9 = missing/blank Phone number present on cover sheet 0 = no telephone number 1 = telephone number listed on cover sheet 9 = missing/blank Comment Check codes = yes, a comment included 9 = no Comment Check codes Comment Check codes Comment Check codes Comment Check codes Edit-History Check Code 0 = Checked, Not changed 1 = Checked, Changed 2 = Checked, Changed, Need New Letter 9 = Not checked yet

17 TRACKING INFORMATION DATA FILE NATIONAL SURVEY OF FAMILIES AND HOUSEHOLDS We are implementing the entry software for tracking information. Column locations will be added at a later date. The Tracking Information File will contain the following data: 1-5 Respondent ID Number 6-6 Check Code 0 = OK 1 = Not OK - Check later 7-9 Respondent 1987/88 Area Code Respondent Telephone Number Number of References provided (Main Interview page 158) First Reference (Main interview page 158) First name Middle name or Initial Last name Suffix (Jr., III, Esq, etc.) Relationship Street Address Apartment or Lot number City State Zip Code Area Code Telephone number Husband's first name Husband's Middle name or Initial Husband's Last name Suffix (Jr., III, Esq, etc.) Second Reference (Main interview page 158) First name Middle name or Initial Last name Suffix (Jr., III, Esq, etc.) Relationship Street Address Apartment or Lot number City State

18 Zip Code Area Code Telephone number Is husband's name blank? (Y/N) First name Middle name or Initial Last name Suffix (Jr., III, Esq, etc.) Third Reference (Main interview page 158) First name Middle name or Initial Last name Suffix (Jr., III, Esq, etc.) Relationship Street Address Apartment or Lot number City State Zip Code Area Code Telephone number Is husband's name blank? (Y/N) First name Middle name or Initial Last name Suffix (Jr., III, Esq, etc.) Is husband's name blank? (Y/N) (Main Interview Q. 670, page 159) First name Middle name or Initial Last name Suffix (Jr., III, Esq, etc.) Is maiden name blank? (Y/N) (Main Interview Q. 670, page 159) First name Middle name or Initial Last name Suffix (Jr., III, Esq, etc.) Respondent's Date of Birth (From Temple Tracking Information Form) Month Day Year Any Degrees Listed? (Y/N) (From Temple Tracking Information Form) AA: degree? (Y/N) School

19 City State Year BA: degree? (Y/N) School City State Year MA: degree? (Y/N) School City State Year DOCT: degree? (Y/N) School City State Year Name of Company or Business (CR if none) (From Temple Tracking Information Form)

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32 Center for Demography and Ecology University of Wisconsin 1180 Observatory Drive, Rm Madison, WI U.S.A. 608/ FAX 608/ requests to: