THE SURVEY OF INCOME AND PROGRAM PARTICIPATION

           THE SEAM EFFECT IN SIPP'S LABOR FORCE DATA:
                DID THE RECESSION MAKE IT WORSE?

                       WORKING PAPER #9308

                       BY:  PAUL RYSCAVAGE
                          CENSUS BUREAU

U.S. DEPARTMENT OF COMMERCE
BUREAU OF THE CENSUS

Presented at the Joint Statistical Meetings, August 9, 1993, in
San Francisco, California.  Paul Ryscavage is a Senior Labor
Economist in the Housing and Household Economic Statistics
Division.  Special thanks go to Caroline Carbaugh of the Computer
and Programming and Applications Staff of the same Division for
the development of the data files used in this analysis.  The
views expressed in this paper are attributable to the author and
do not reflect those of the Census Bureau. 

                 THE SEAM EFFECT IN SIPP'S LABOR FORCE DATA: DID THE
                    RECESSION MAKE IT WORSE?

                               by

                         Paul Ryscavage
                    U.S. Bureau of the Census

I.   Introduction

     The seam effect is a well-known phenomenon associated with
longitudinal surveys, such as the Survey of Income and Program
Participation (SIPP).  The "seam" derives its name from the
abutment of consecutive survey reference periods, about which
survey enumerators collect various kinds of information in 
interviews.  The "seam effect" is observed when the information
collected for the end of one reference period (based on one
interview) is compared to the information collected for the
beginning of the next reference period (based on another 
interview).  Survey researchers have found that there is a
tendency for a greater amount of change in information to be
reported at the seams of reference periods than within reference
periods.

     In the context of SIPP, in which reference periods consist
of four months, the seam effect has been observed and documented
in SIPP's labor force, income, and program participation data
(e.g., Martini, 1989; Burkhead and Coder, 1985; Marquis and
Moore, 1990).  Changes are over-reported in status (such as
participation in the Food Stamp program or a labor force
activity) and amounts (such as the value of Food Stamps) for a
pair of months at the seam of the reference period.  In this case
data have been obtained from two different interviews.  Changes
are under-reported, however, in such data items for a pair of
months not at the seam of the reference periods.  In this case
the data are obtained from only one interview.  

     The impact of the seam effect on SIPP cross-sectional
estimates, however, may be small because of SIPP's sample design
(Jabine et al, 1990).  In any two consecutive months, over-
reporting of changes and under-reporting of changes may tend to
cancel each other out.  This is because only one-fourth of the
SIPP sample would have provided data items in two separate
interviews while three-fourths of the sample would have provided
data items in only one interview.  Indeed, some who have
evaluated research in the area of program participation have
suggested as much (Singh, Weidman, Shapiro, 1989).

     This research has been corroborated to some extent by a
recent examination of particular cross-sectional estimates from 
SIPP panels placed in the field by the Census Bureau during the
1980's (Ryscavage, 1992a).  Many of the cross-sectional estimates
tracked benchmark data with some consistency.  With respect to
labor force estimates, SIPP estimates showed strong increases in
employment and sharp decreases in unemployment during the 1980's. 
In fact, an analysis of the SIPP labor force data from the 1990
panel, which covers the downturn in economic activity that began
in mid-1990, indicated a similar deterioration in the labor
market as did data from the Bureau of Labor Statistics' (BLS)
Current Population Survey (CPS) (Ryscavage, 1992b). 

     Much less is known about the impact of the seam effect on
SIPP's longitudinal data, other than it has an obvious effect on
longitudinal measures such as gross flows, transition rates, and
duration estimates.  But its presence in the data has been
monitored almost exclusively with data from SIPP panels fielded
during the 1980's, a period of robust economic growth.   During
this period, economic events were influencing particular
longitudinal changes in unique ways, ways which would be
consistent with what SIPP cross-sectional estimates were
indicating.  In the 1990-91 period, however, the economic events
changed and presumably so did their influence on longitudinal
changes (this no doubt occurred since SIPP's cross-sectional
estimates reflected a weakening economy).  The question becomes,
then, given the change in economic climate and the differences in
longitudinal flows, what happened to the seam effect?  Is the
seam effect responsive to changes in the business cycle or is it
immune? 

     In this paper, an attempt is made to answer these questions
in the context of SIPP labor force data.  Labor force data, of
course, are very sensitive to changes in the business cycle.  The
paper is organized as follows: In Section II the conceptual
argument behind the above questions is further elaborated; in
Section III a discussion of the SIPP data files used to address
the questions is provided; Section IV contains the empirical
results of the investigation; and in Section V, the implications
of the empirical findings are discussed.

II.  Why Might the Seam Effect Vary With the Business Cycle

     If we consider the seam effect in the context of labor force
activity it would be intuitive to assume that it is the result of
"multiple" seam effects arising from the different labor force
transitions that can occur between two periods of time.  Consider
that labor force activity can be classified at a point in time
into three mutually exclusive statuses: employed (E), unemployed
(U), and not in the labor force (N).  Between two points in time,
t and t + 1, a variety of transitions in these statuses are
possible, as is depicted in the matrix below: 

                          Time (t + 1)

Time (t)         EmployedUnemployed     Not in labor force
Employed                               EE   EU             EN
Unemployed       UE          UU                           UN
Not in labor
 force               NE     NU                              NN

Six changes in labor force status are possible between these two
time periods.  Theoretically, in periods of economic expansion
when employment is increasing and unemployment decreasing, the UE
and NE transitions would exceed the EU and EN transitions since
the stock of employed persons is rising and stock of unemployed
persons is falling; in periods of economic contraction the
reverse situation would prevail.    

     When transition rates such as these were estimated by
Martini (1989) using SIPP data from the 1984 and 1985 panels,
some relevant facts were revealed: First, transition rates varied
and the rates from U to E and U to N were considerably higher
than all other estimated transitions; second, all transition
rates occurring at the seams of SIPP's reference periods were
much higher than those occurring within reference periods; and
third, and most importantly, the relationships between transition
rates measured at the seams of reference periods and within
reference periods varied.  With respect to this last point, while
the UE rate at the seam was almost twice as large as that within
the reference period, the UN transition was around six or seven
times greater at the seam then within the reference period and
the NU rate was four or five times higher at the seam.  This
latter finding indicates that for whatever the reason or reasons,
some labor force transitions are more likely to be "heaped" at
the seams of reference periods than others.  Therefore, shifts in
the pattern of labor force flows, provoked by changing labor
market conditions alone, could affect the seam phenomenon.

     An example may further clarify this point.  Imagine a tiny
economy composed of 100 workers and a SIPP-like survey that
produces a seam effect on the inflow and outflow of workers. 
Further, consider that employment is growing and that the inflow-
outflow of jobs has the following pattern as recorded in SIPP:

                   Month-to-Month Transitions

GROWING   Total
                jobs1->2       2->3     3->4       4->1     % at
                                                                                                                                                                                                                                                                                                                                                                                                       Seam

Net jobs     100    108         116     124         130
Inflow        50     10          10      10        20         40%
Outflow       20      2           2       2        14         70%  

In this example, of the 50 inflow transitions, 40 percent were
caught at the seam but of the 20 outflow transitions, 70 percent
were reported at the seam.  Of all the transitions, therefore, 
49 percent (34/70 x 100) took place at the seam.  Now consider a
declining economy with a different inflow-outflow pattern but
with the same probabilities that the transitions will be observed
at the seam:

                   Month-to-Month Transitions

DECLINING Total
                jobs1->2       2->3     3->4       4->1     % at
                                                                                                                                                                                                                                                                                                                                                                                                       Seam
Net jobs  100         99       98         97       70
Inflow     20          4        4          4       8           40%
Outflow    50          5        5          5       35         70%

Here we see net jobs declining by 30 workers and the same
proportion of inflow and outflow transitions being caught at the
seam.  BUT because the inflow-outflow pattern of jobs has
changed, the proportion of all transitions being reported at the
seam (the "seam effect") rises to 61 percent (43/70 x 100). 

     This oversimplified example (designed to be consistent with
Martini's findings), of course, suggests that the seam effect
would be much higher in an economy that is undergoing declining
employment.  A priori, our suspicion is that the seam effect
would have been exacerbated by the decline in the economy in the
1990-91 period.  This is because of the greater likelihood that
many transitions between UN and NU would have taken place during
this time and these particular transition have a much greater
probability than others to be reported at the seam.

     The measurement error process involved with labor force
activity and the seam effect is very complicated and Martini
(1989) has distinguished three types of errors that may be
associated with it.  These are: 1) omitting periods of
employment, unemployment, or no labor force activity; 2)
incorrectly reporting the start and end dates of periods of labor
force activity or inactivity; and 3) errors in classifying
periods of employment, unemployment, or no labor force activity. 
The important point for this paper is that whatever the
measurement error process, a change in the mix of labor force
transitions could result in a change in the proportion of labor
force transitions being reported at the seams of reference
periods. 

III. The SIPP Data Files

     SIPP labor force data for the first five waves of
interviewing from the 1987 panel and 1990 panel were used in the
analysis providing four sets of seam months.  (The reason for
using only the first five waves was that at the time of this
writing only a five-wave longitudinal file was available from the
1990 panel.)  This file, nevertheless, covered the 20-months in
which the economy reached its cyclical peak (mid-year of 1990) 
and then began to contract (gross domestic product declined in
the second-half of 1990 and the first-quarter of 1991) (Council
of Economic Advisers, 1993).  With respect to the labor market,
between the second quarters of 1990 and 1991, employment fell by
1.2 million persons and unemployment rose by 1.8 million (U.S.
Department of Labor, 1992). 

     For the sake of comparability, only the first five waves of
the 1987 SIPP panel were used in the analysis.  This time period
was marked by quite different economic circumstances.  Gross
domestic product grew at an average rate of 4.2 percent per
quarter (seasonally adjusted) between the first quarter of 1987
and second quarter of 1988, and, on an annual average basis,
employment increased by 2.5 million workers and unemployment
dropped by 724,000 persons between 1987 and 1988 (Council of
Economic Advisers, 1993).  Consequently, the economic conditions
under which the first five waves of the 1987 and 1990 panels were
conducted were markedly different.

     Both files contain only individuals who were fully
interviewed for the entire panel, in other words, persons who
were assigned positive weights.  Naturally, attrition bias is of
concern.  According to the Census Bureau, however, the amount of
sample loss in the first five months of the 1990 panel was not
substantially different from that experienced in the 1987 panel. 

     All estimates presented are weighted, although there is a
difference in the types of weights used.  In the 1987 panel
longitudinal weights have been used, while in the 1990 panel,
1990 calendar year weights are applied but only to fully
interviewed persons.   Longitudinal weights had not yet been
developed for the 1990 five-wave panel file.   While this creates
inconsistency in estimated levels, it does not necessarily affect
proportions or rates which is the analytical metric of this
paper. 

     Because of SIPP's staggered sample design, it is important
to remember how the data are interpreted with respect to time. 
For example, the 4th and 5th, 8th and 9th, 12th and 13th, and
16th and 17th months are "seam" months in SIPP in that they
represent the last month of a reference period and abut the first
month of the following reference period.  They DO NOT correspond
to the same calendar month: This is because of the staggered
pattern of the four rotation groups.  In other words, the first
seam in the 1987 panel for the second rotation group occurred
between January and February 1987; the first seam for the third
rotation occurred between February and March 1987; the first seam
for the fourth rotation group occurred between March and April
1987, and for the first rotation group it occurred between April
and May 1987. 

IV. Labor Force Transitions at the Seam

     Two types of labor force variables unique to SIPP are used
to examine the seam effect.  The first is a simple variable that
identifies whether or not an individual held a wage or salary job
at any time in a particular month.  We refer to transitions
involving this variable "job transitions."  The second variable
is a more complicated variable.  It characterizes an individual's
labor force status during the course of the month, that is,
whether the person had a job, or had a job and also spent some
time looking for work, or had a job, was on layoff, and was also
outside the labor force, and so on, all within a single month. 
There are eight possible statuses in SIPP and transitions
associated with these variables will be referred to as "status
transitions."  Both of these labor force variables are commonly
used by researchers in conjunction with other information
collected in the SIPP panels.

Job Transitions.  Figure 1 displays the by now classic picture of
the seam effect when portrayed as the probability of a change
taking place in an individual's job status, in other words,
moving from no job to a job, or from a job to no job, or from one
job to another job.  Clearly, the likelihood of job changing is
higher in a pair of seam months, that is, between the end of one
reference period and the start of another.  Roughly speaking, the
likelihood of a change in job status taking place is more than
three times as great at the seam then it is within the reference
period.

     With respect to the seam months, the percentages of
individuals involved in job changes were not significantly
different between the panels, except for the second seam where
the likelihood of a change was higher in 1987 than in 1990. 
While this is of interest and one way of looking at the seam
effect, for this paper our interest is in whether or not there
was a difference in the proportion of all job transitions being
reported at the seam in a period of economic recession and a
period of economic expansion.    

     Table 1 presents distributions of the total number of job
transitions taking place in the 1987 and 1990 panels by the kind
of job transition, as well as the proportion taking place at the
seam of the reference periods.  As indicated in the top panel of
the Table, there was not a great deal of difference in the
distribution of transitions by type.  However, the changes that
did occur were consistent with a weakening job market.  The
proportion of transitions that involved a change from having a
job to not having a job rose from 34.1 to 35.1 percent; the
proportion of transitions involving a no job to job movement fell
from 35.9 percent to 33.9 percent.  The difference in proportion
involving a movement from one job to another was not
statistically significant.

     The bottom panel of Table 1 shows the proportion of the
total transitions as well as the transitions by type that were
reported taking place between the seam months.  Overall, a
somewhat greater proportion of transitions were observed in the
seam months in the 1990 panel than was the case in the 1987
panel--54.9 vs. 51.4 percent.  When the types of transitions are
examined, it appears that all types were more likely to be
reported at the seam (however, the difference in the job-to-job
transition was not statistically significant).  

     This finding provides some preliminary evidence that the
overall seam effect did worsen in the 1990.  However, it also
indicates that this increase was not necessarily due to one type
of transition dominating another.  Indeed, it weakens the
argument that the recession had caused one type of transition
pattern to influence the overall seam problem.  It appears that
the problem was worse regardless of the type of transition.

     (These data are also suggestive of some other aspects of the
seam phenomenon.  For whatever the reason or reasons and
regardless of panel, individuals who report moving from one job
to another job have a great tendency to report this at the seam
of the reference periods.  On the other hand, persons moving into
jobs are less likely to report these events occurring at the
seams of reference periods.  Whether or not this has something to
do with the relative saliency of the events is certainly a topic
for further investigation.)

     Because economic downturns affect population groups
differentially it was decided to analyze what happened to the
seam effect across three age-sex groups, groups which have
different patterns of labor force participation as well as
unemployment experiences.  The first group examined was young
persons age 16 to 24.  Typically, they have a very dynamic labor
force activity pattern, but the data examined showed no
statistically significant shifts in the composition of their job
transitions between the 1987-88 period and the 1990-91 period. 
In the 1990 SIPP panel, however, there was a somewhat greater
likelihood for young persons' job changes to take place at the
seam, as shown in Table 2.  This was particularly true for those
young persons who did not have a job in one month but moved into
one in the next month.  The proportion of these no job-to-job
transition recorded at the seams in the 1990 panel was 43.2
percent compared to 38.0 percent in the 1987 panel.

     Adult men age 25 to 64 were hit hard by the recession in
1990-91 (of the three groups, their unemployment rate, as
measured in the CPS, rose the most).  Indeed, the SIPP data in
Table 3 show "job-to-no job" transitions rose as a proportion of
all transitions from 32.4 percent in the 1987 panel to 34.9
percent in the 1990 panel.  The changes in the other transition
possibilities were not statistically significant.  Interestingly,
the proportion of these types of transitions reported at the seam
were no higher in that panel than in the earlier panel.  However,
men moving from job-to-job or from no job to a job did tend to
report greater changes in the seam months in the 1990 panel than
in the 1987 panel.  And these types of changes are more
characteristic of an expanding labor force.  Consequently, this
is additional evidence that although the seam effect had
increased, it may have not necessarily been associated with weak
labor market conditions and labor market transition patterns
typically associated with this type of market.

     The last group examined was adult women age 25 to 64. 
Consistent with deteriorating labor market conditions the
proportion of women's transitions accounted for by "no job to
job" declined from 37.1 percent to 33.8 percent (Table 4).  But
not consistent with deteriorating labor market conditions was the
increase in the proportion of transitions occurring between jobs. 
This transition pattern rose from 26.4 to 29.9 percent.  

     The women's overall seam effect was also significantly
higher in the 1990 panel, as was the case for young persons and
adult men.  Transitions involving a movement from a job to no
job, which did not change in importance between panels, were much
more likely to be recorded in the seams months.   

Status Transitions.  The status transitions used in this analysis
provide a somewhat more refined look at the nature of changes in
labor force activity and are based on SIPP employment status
recodes (ESR's).  For example, a person may move from having a
job one month and no job the next, but in that subsequent month
he or she may have looked for another job or dropped out of the
labor force, or both.  SIPP uses eight ESR's to characterize an
individual's labor force activity in the course of a month:

ESR 1--             With job entire month, worked all weeks.
ESR 2--        With job entire month, missed one or more weeks
               but not because of a layoff.
ESR 3--        With job entire month, missed 1 or more weeks
               because of layoff.
ESR 4--        With job part of month, but not because of layoff
               or looking for work.
ESR 5--        With job part of month, some time spent on layoff
               or looking for work.
ESR 6--        No job in month, spent entire month on layoff or
               looking for work.
ESR 7--        No job in month, spent part of month on layoff or
               looking for work.
ESR 8--        No job in month, no time spent on layoff or
               looking for work.
As with the more traditional labor force statuses (employed,
               unemployed, and not in the labor force) in which six unique
               transitions can be identified between two periods of time, so too
               can transition paths be identified from the ESR's.  However,
               there are many more than six possibilities.

     In Table 5, we identify six transition possibilities (and an
all other category) which attempts to replicate the more
traditional labor force transitions.  The first, ESR 1 to 3, 5-7, 
identifies a movement of a fully employed worker in one month to
a status in a month containing some unemployment; the second, ESR
3, 5-7 to 1, represents the reverse situation in which a
partially unemployed person is moving into a job for the entire
month.  The third transition, ESR 8 to 1,2,4, represents a person
moving from outside the labor force to a status of full or
partial employment; the fourth, ESR 1,2,4 to 8, is the reverse
flow of someone leaving employment to outside the labor force. 
The fifth transition, ESR 8 to 6,7, represents the transition of
a worker from outside the labor force to some amount of active
job search; and the sixth, ESR 6,7 to 8, represents the movement
of someone dropping out of the labor force.

     As shown in the upper panel of the Table 5, these
transitions accounted for slightly more than 50 percent of all
the transitions that took place in the 1987 and 1990 panels. 
What is also shown is that there was a statistically significant
shift in the proportion of ESR 1 to 3, 5-7 transitions involving
a movement from employment to unemployment--from 8.5 to 10.1
percent--which would have been anticipated given the slackening
demand in the labor market.   The other identified transitions,
however, showed very little change.  The residual category--
composed of all other possible transitions--declined slightly in
importance from 46.3 to 45.2 percent.   

     In the bottom half of the panel is shown the proportion of
these transitions that were reported at the seams of the
reference periods.  Overall, there was a statistically
significant increase in the seam problem (as was the case with
job transitions). While increases occurred in all the transition
categories, most of them were small and only three were
statistically significant.  Two of these involved the movement of
persons from outside the labor force to employment or
unemployment.  The all other transition category also showed a
greater likelihood of having transitions reported at the seam. 
(It is of interest to note the difference in the proportions of
transitions reported at the seam when the transition involves a
movement between not in the labor force and unemployment (or vice
versa) and the "all other" transitions.  In the former case,
upwards of 60 to 70 percent are reported as occurring at the
seam, but in the latter slightly less than 30 percent.  Of
course, the former comprised a much smaller proportion of all
transitions than the latter.)
               Transitions from employment to unemployment (ESR 1 to 3,5-
7), which had increased in importance in the 1990 panel, were no
more likely to be reported at the seam in that panel than they
were in the 1987 panel.  Consequently, the impact of their shift
in importance between the 1987 and 1990 panels, relative to other
transitions, had presumably little effect on the overall seam
problem.

A Shift-Share Analysis.  To more rigorously determine the
quantitative impact of shifts in job and status transitions on
the overall seam effect between the 1987-88 period and 1990-91
period, a simple shift-share analysis was carried out on both
types of transitions.  This analysis involves, first, holding
constant the distribution of transitions as they were in the 1987
panel, but then applying the actual percentages of transitions
reported at the seams in the 1990 panel and then recalculating
the overall seam effect.  This yields the effect of the shift in
composition of the transitions on the overall seam effect.  

     Thus, the seam effect in 1990 can be expressed as follows,
where S  represents the overall effect, p   the relative weight
of the ith transition and s  is the proportion of transition i
observed at the seam:

                              S=ps

To compute what the overall seam effect would have been if shifts
in the composition had not taken place the following expression
is calculated where the p  are the relative weights of the
transitions in the 1987 panel. 

                              S*=ps

     The second part of the analysis involves holding constant
the seam effects on the individual transitions as of the 1987
panel and applying these to the actual distribution of
transitions that resulted in the 1990 panel.  Thus, if the seam
effects for individual transitions had not changed between the
panels, the overall seam effect would be calculated as

                              S**=ps

     Table 6 presents the results of this simple exercise.  In
terms of the job transitions, it shows that the overall seam
problem increased not because of shifts in the composition of job
transitions induced by the recession, but more generally as a
result of higher seam effects among the various transitions.  If,
indeed, the same proportions of transitions had been reported at
the seams in the 1990 panel as in the 1987 panel, virtually the
same overall seam effect would have resulted, despite the much
different economic environment.  In terms of the status
transitions, this fact is demonstrated even more convincingly.
V. Implications

     The economic situation in this country changed dramatically
between the late 1980's and early 1990's.  As unfortunate as this
was for millions of Americans, it does provide survey researchers
involved with the collection of socio-economic data with an
opportunity to examine how their data collection operations
perform under different economic conditions.

     This paper looked at one problem concerning the Survey of
Income and Program Participation--and that was its seam problem. 
The phenomenon of over-reporting change at the seams of SIPP's
reference periods and an under-reporting of change during its
reference periods has been observed in many of the SIPP panels in
the 1980's.  An obvious question is how did this problem behave
in the 1990 panel when the Nation's entered a period of much
slower economic growth.

     The analysis was conducted exclusively with labor force data 
from the first five waves of interviewing in SIPP's 1987 and 1990
panels.  The seam problem had increased with respect to these
data in the 1990 panel relative to the 1987 panel, and an
argument was made that this might have been the result of shifts
in the composition of various labor force transitions,
transitions with a greater likelihood of being reported at the
seam.  After investigating the various transitions, both with
respect to the changes involving jobs and changes involving labor
force statuses, it was concluded that greater "seam reporting" of
transitions had occurred across many different transitions
irrespective of their association with slackened labor demand.

     Two directions for further research are warranted.  First,
it would be useful to observe whether the seam problem was higher
in the 1990 panel in terms of other variables, such as program
participation and amounts received.  Second, and more
challenging, is to explore why survey respondents in the 1990
panel became more inclined to report changes in their labor
market activity in seam months.  Because of its large sample size
and because of the time period it covers, the 1990 panel will
become an important data source for researchers.  It would
behoove survey researchers, therefore, to better understand the
increased seam problem it contains.   

REFERENCES

Burkhead, Dan and Coder, John, "Gross Change in Income Recipiency
for the SIPP," Proceedings of the Social Statistics Section,
American Statistical Association, pp. 351-356, 1985.

Council of Economic Advisers, Economic Report of the President,
(Washington, D.C.:USGPO), January, 1993.

Jabine, Thomas B., King, Karen F., and Petroni, Rita J., SIPP
Quality Profile, Bureau of the Census, May, 1990.

Marquis, Kent, and Moore, Jeffrey, "Measurement Errors in the
Survey of Income and Program Participation (SIPP) Program
Reports,"  Proceedings of the 1990 Annual Research Conference,
U.S. Bureau of the Census, pp. 721-745, August, 1990. 

Martini, Alberto, "Seam Effect, Recall Bias, and the Estimation
of Labor Force Transition Rates From SIPP," Proceedings of the
Section on Survey Research Methods, American Statistical
Association, pp. 387-392, August, 1989.

U.S. Department of Labor, Bureau of Labor Statistics, Employment
and Earnings, January, 1992.

Ryscavage, Paul, "The 1990-91 Recession Through the Lens of
SIPP," Internal Census Bureau memorandum from Paul Ryscavage to
Charles Nelson (HHES Division), November 18, 1992a.

Ryscavage, Paul, "Slipping Into the Recession: How Well Did SIPP
Labor Force Data Reflect It?"  Proceedings of the Section on
Social Statistics, American Statistical Association, 1992b
(forthcoming). 

Singh, Raj, Weidman, Lynn, and Shapiro, Gary, "Quality of SIPP
Estimates," Individuals and Families in Transition: Understanding
Change Through Longitudinal Data, Bureau of the Census, pp. 301-
332, 1989.

Table 1.            Total Job Transitions by Type and Percent Occurring at
the Seam of the Reference Periods, 1987 SIPP Panel and 1990 SIPP
Panel 

(In percent)

Type of Transition                     1987 Panel 1990 Panel

                        TOTAL TRANSITIONS

Total                                                                           100.0100.0

     Job-to-Job                               30.0 31.0

     Job-to-No Job                      34.1        35.1*

     No Job-to-Job                      35.9        33.9*

             PERCENT OF ALL TRANSITIONS AT THE SEAM

Total                                                                            51.4 54.9*

     Job-to-Job                               60.8 62.6

     Job-to-No Job                      53.2        56.3* 

     No Job-to-Job                      41.9        46.4*

*    The difference between the estimate for the 1990 panel and
that for the 1987 panel was statistically significant at the 10-
percent level.

Table 2.            Total Job Transitions of Persons Age 16 to 24 by Type
and Percent Occurring at the Seam of the Reference Periods, 1987
SIPP Panel and 1990 SIPP Panel

(In percent)

Type of Transition                     1987 Panel 1990 Panel

                        TOTAL TRANSITIONS

Total                                                                           100.0100.0

     Job-to-Job                               30.0 30.8

     Job-to-No Job                      32.4        32.8

     No Job-to-Job                      37.6        36.4

             PERCENT OF ALL TRANSITIONS AT THE SEAM

Total                                                                            49.3 52.5*

     Job-to-Job                               60.9 62.1

     Job-to-No Job                      51.9        53.6 

     No Job-to-Job                      38.0        43.2*

*  See Table 1.

Table 3.            Total Job Transitions of Men Age 25 to 64 by Type and
Percent Occurring at the Seam of the Reference Periods, 1987 SIPP
Panel and 1990 SIPP Panel

(In percent)

Type of Transition                     1987 Panel 1990 Panel

                        TOTAL TRANSITIONS

Total                                                                           100.0100.0

     Job-to-Job                               36.0 34.8

     Job-to-No Job                      32.4        34.9*

     No Job-to-Job                      31.6        30.1

             PERCENT OF ALL TRANSITIONS AT THE SEAM

Total                                                                            53.5 57.2*

     Job-to-Job                               59.6 63.7*

     Job-to-No Job                      55.2        56.7 

     No Job-to-Job                      44.7        50.5*

*  See Table 1.

Table 4.            Total Job Transitions of Women Age 25 to 64 by Type And
Percent Occurring at the Seam of the Reference Periods, 1987 SIPP
Panel and 1990 SIPP Panel

(In percent)

Type of Transition                     1987 Panel 1990 Panel

                        TOTAL TRANSITIONS

Total                                                                           100.0100.0

     Job-to-Job                               26.4 29.9*

     Job-to-No Job                      36.3        36.4

     No Job-to-Job                      37.1        33.8*

             PERCENT OF ALL TRANSITIONS AT THE SEAM

Total                                                                            52.1 55.1*

     Job-to-Job                               62.0 61.8

     Job-to-No Job                      53.1        57.5* 

     No Job-to-Job                      44.5        46.6

* See Table 1.

Table 5.            Total Status Transitions by Type and Percent Occurring
at the Seam of the Reference Periods, 1987 SIPP Panel and 1990
SIPP Panel

(In percent)

Type of Transition 1/                           1987 Panel1990 Panel

                        TOTAL TRANSITIONS

Total                                                                                                         100.0100.0

     ESR 1               to ESR 3, 5-7  8.5                      10.1*
     ESR 3, 5-7     to ESR 1          11.2                         11.1
     ESR 8               to ESR 1, 2, 4 10.8                   10.5
     ESR 1, 2, 4    to ESR 8          12.3                         12.2
     ESR 8               to ESR 6, 7  5.9                             5.9
     ESR 6, 7         to ESR 8       5.0                                5.1
     All other                                                        46.3 45.2*     

            PERCENT OF ALL TRANSITIONS AT THE SEAM   

Total                                                                                                          38.5 40.2*
     ESR 1               to ESR 3, 5-7 34.1                      34.5
     ESR 3, 5-7     to ESR 1          37.6                         37.9
     ESR 8               to ESR 1, 2, 4 46.3                   49.9*
     ESR 1, 2, 4    to ESR 8          54.9                         56.8
     ESR 8               to ESR 6, 7 52.8                            59.0*
     ESR 6, 7         to ESR 8      68.4                               68.2
     All other                                                        28.2 29.7* 

*  See Table 1.

1/   The ESR definitions are as follows:
ESR 1--             With job entire month, worked all weeks.
ESR 2--        With job entire month, missed one or more weeks
               but not because of a layoff.
ESR 3--        With job entire month, missed 1 or more weeks
               because of layoff.
ESR 4--        With job part of month, but not because of layoff
               or looking for work.
ESR 5--        With job part of month, some time spent on layoff
               or looking for work.
ESR 6--        No job in month, spent entire month on layoff or
               looking for work.
ESR 7--        No job in month, spent part of month on layoff or
               looking for work.
ESR 8--        No job in month, no time spent on layoff or
               looking for work.

Table 6.            Changes in Overall Seam Effects With Job Transitions
and Status Transitions When the Composition of Transitions and
Individual Seam Effects are Held Constant as of the 1987 Panel

Effects                                                                 1987 Panel1990 PanelChange

JOB TRANSITIONS

Actual Change                                                            51.454.93.5*

     Constant 1987 Composition     51.4                  54.63.2*

     Constant 1987 Individual       51.4               51.7 0.3
       Seam Effects

STATUS TRANSITIONS

Actual Change                                                            38.540.21.7*

     Constant 1987 Composition     38.5                  40.21.7*

     Constant 1987 Individual       38.5               38.5 0.0
       Seam Effects

*  See Table 1.