ISTAT - Italian National Institute of Statistics Labour Force Survey Division Unit “Methods for...

ISTAT - Italian National Institute of Statistics

Labour Force Survey Division

Unit “Methods for LFS data treatment”

European Conference on Quality in Official Statistics – Q2010

3 - 6 May 2010 - Helsinki ( Finland )

Longitudinal data from Italian Labour Force Survey

Barbara Boschetto [email protected]

Antonio R. Discenza [email protected]

Francesca Fiori [email protected]

Carlo Lucarelli [email protected]

Simona Rosati [email protected]

mailto:[email protected]





European Conference on Quality in Official Statistics – Q2010 3 - 6 May 2010 - Helsinki

Outline of the presentation

Issues related to the production of longitudinal microdata and gross flows estimates consistent with the official quarterly estimates

a specific focus is devoted to the weighting procedure, which account both for a suitable reference population and compensate for the total non-response at subsequent waves

the most relevant methodological problems addressed are:

definition of a suitable reference population for the longitudinal sample

longitudinal non-responses and eligibility

coherence between cross-sectional and longitudinal estimates


Quarter 4 2000 A2 B1

Quarter 1 2001 B2 C1

Quarter 2 2001 C2 D1

Quarter 3 2001 A3 D2 E1

Quarter 4 2001 A4 B3 E2 F1

Quarter 1 2002 B4 C3 F2 G1

Quarter 2 2002 C4 D3 G2 H1

Quarter 3 2002 D4 E3 H2 I1

Quarter 4 2002 E4 F3 I2 L1

ROTATION GROUPREFERENCE PERIOD

Household rotation scheme 2-2-2 in the Italian LFS

50% of the sample overlaps after 1 quarter and 1 year


Net changes in quarterly levels

are the final result of a high number of gross flows of different nature and different size

Demographic flows: – Children aged 15 entering working age– Deaths– Internal and International migration

Labour status transitions: – Flows between the three main activity states

(employment, unemployment and inactivity)


GROSS LABOUR MARKET FLOWS

OCCUPATIEMPLOYMENT

PERSONE IN CERCA DI

OCCUPAZIONEUNEMPLOYMENT

NON FORZE DI LAVORO

INACTIVE

CANCELLATI DALL'ANAGRAFE e

MORTI

DEATHS AND PEOPLE LEAVING MUNICIPALITIES

ISCRITTI ALL'ANAGRAFE e

15ENNI

CHILDREN AGED 15 AND PEOPLE ENTERING

MUNICIPALITIES


Choice 1: the reference population is equal to the population of the initial quarter

Ideally, longitudinal data from LFS should represent the whole initial population.

However, the initial population actually change during the period of observation because of deaths and internal and international migrations.

Thus longitudinal data could represent the whole initial population only if the LFS was designed like a “proper” panel, in which all the individuals in the initial sample were “followed” for a new interview at a later stage.

This means that the information must be collected also on people moving to another municipality or to another country.

Actually, information for those persons who left the country during a given period is usually never available.


Figure 1: Scheme for a “desirable” complete matrix with stocks and gross flows from LFS .

Employed

Unemployed ( T ) ( D ) ( L ) ( S1 )

Inactive

Total

( C )

( E )

( S2 )

Children age 15

Total

Labour Status at the end of the period

Inactive

Total cross- sectional Population at the

beginning of period (15 and over)

Total cross- sectional Population at the end of period (15 and over)

Total Longitudinal Population

(15 and over) Employed Unemployed

People Entering the Country (15 and over)

Lab

ou

r S

tatu

s at

th

e b

egin

nin

g o

f th

e p

erio

d

People Leaving the

Country (15 and over)

Deaths


Choice 2: the reference population is a specific longitudinal population

However, even the population resident in a country at the beginning of the period, which is still resident in the country at the end of the reference period, can experience movements to and from the different municipalities (internal migration).

Usually, in the LFS, people moving out of the household, across the country, are not “followed” for re-interview.

Is it still correct to use the initial population as the reference population ?

In fact, in the longitudinal sample we have information only about those individuals still resident in the same municipality at the end of the period.

The longitudinal component (sub-sample) of the Italian LFS requires thus the specification of a suitable reference population.


Choice 2: the reference population is a specific longitudinal population

•If we weight the longitudinal sample to the initial population we make a very strong assumption: the behaviour of individuals which moves out of the municipality from one wave to another is similar to those who do not move.

•We have, thus, at least two problems:

Actually, at least in Italy, these two groups are very different

Moreover, if we use the longitudinal microdata to produce flow estimates, there are no records of individuals moving to other regions/country and/or dying (whereas they do exist in the population).


Definition of longitudinal population

The Longitudinal Population is defined in Italy as the population which is resident in the same municipality for the entire 12 months period

excluding

– deaths

– those who have moved to other Italian municipalities (change of residence)

– Migrants to other countries

•It is computed from population register data on resident population; it is classified by broad age groups, geographical area (NUTS III) and nationality (Italian, EU, non-EU)

•It is fully consistent with the reference population of EU-LFS quarterly data was also ensured.


Figure 1: Scheme for the two transition matrices referred to the longitudinal population and to internal migrants..

Employed

+ Unemployed

Inactive

Total La

bo

ur

Sta

tus

at

the

b

eg

inn

ing

of

the

pe

rio

d

Population which moves across the

country (15 and over)


Employed Unemployed Inactive Total

Employed

Unemployed ( T )

Inactive

Total La

bo

ur

Sta

tus

at t

he

be

gin

nin

g o

f th

e p

eri

od

Total Longitudinal Population

(15 and over)


Employed Unemployed Inactive Total

Employed

Unemployed ( TL )

Inactive

Total

Longitudinal Population

(15 and over) Employed Unemployed

La

bo

ur

Sta

tus

at

the

b

eg

inn

ing

of

the

pe

rio

d

Total


Inactive


Figure 3: Scheme for a “actual” complete matrix with stocks and

gross flows from Italia LFS .

The longitudinal estimates must be consistent with the “official” estimates provided by the cross-sectional samples (the full sample) at the beginning and at the end of the observed period.

Using specific constraints in the calibration procedure used to weight longitudinal sample it is possible to reduce the risk of obtaining inconsistent results.

Employed

Unemployed ( TL ) ( D ) ( LM ) ( S1 )

Inactive

Total

( C )

( EM )

( S2 )

Total cross- sectional Population at the

beginning of period (15 and over)

Total cross- sectional Population at the end of period (15 and over)

Longitudinal Population (15 and over)

Employed Unemployed

People Moving Across or Entering the Country (15 and over)

La

bo

ur

Sta

tus

at t

he

be

gin

nin

g o

f th

e p

eri

od

People Moving Across or Leaving

the Country (15 and over)

Deaths

Children age 15

Total


Inactive


Longitudinal non-responses and eligibility

A very important aspect of the longitudinal component of the LFS is usually affected by unit non-response in subsequent waves, such as: Municipality non-response: some (very small) municipalities are

substituted in July at the beginning of a new annual survey cycle and some others may, for different reasons, fail to provide the interviews in subsequent waves;

Household non-response: all the members of the household do not fill in the questionnaire because they refuse to respond;

Individual non-response: some members of the household do not fill in the questionnaire because they refuse to respond, or they cannot be contacted or left the household to create a new household in the same municipality.

Unit non-response may produce bias if non-respondents have significantly different labour features with respect to respondents.


Figure 4: Classification of individuals from the initial sample and eligibility in the Italian LFS (in presence of longitudinal non-response).

PRESENT IN THE INITIAL

SAMPLE

REPRESENT THE INITIAL

POPULATION

YES ( b )

YES

YES ( a )

YES

PRESENT IN THE INITIAL

SAMPLE

REPRESENT THE INITIAL

POPULATION

LONGITUDINAL LINK

YES ( b )

YES

NO

T

MA

TC

HA

BL

EM

AT

CH

AB

LE

INITIAL QUARTER

YES ( a )

YES

NO

FINAL QUARTER

PRESENT IN THE FINAL SAMPLE

NO

T E

LIG

IBL

E F

OR

LO

NG

ITU

DIN

AL

S

AM

PL

E

NO

FINAL QUARTER

CLASSIFICATION OF INDIVIDUALS FROM FINAL SAMPLE

INDIVIDUALS STILL RESIDENT

IN THE SAME MUNICIPALITY

( c )

EL

IGIB

LE

FO

R L

ON

GIT

UD

INA

L S

AM

PL

E

INDIVIDUALS NOT ANYMORE

RESIDENT IN THE SAME

MUNICIPALITY (EXIT THE INITIAL

POPULATION) ( d )

PRESENT IN THE FINAL SAMPLE

RESPONDENTS ( e )

YES

REFUSALS ( f )

NO

UNREACHEABLE ( g )

NO

INTERNAL MIGRATION (TO

ANOTHER MUNICIPALITY)

NO

INTERNATIONAL MIGRATION (TO

ANOTHER COUNTRY)

NO

DEATHS NO

FINAL QUARTER

CLASSIFICATION OF INDIVIDUALS FROM FINAL SAMPLE

INDIVIDUALS STILL RESIDENT

IN THE SAME MUNICIPALITY

( c )

EL

IGIB

LE

FO

R L

ON

GIT

UD

INA

L S

AM

PL

E

INDIVIDUALS NOT ANYMORE

RESIDENT IN THE SAME

MUNICIPALITY (EXIT THE INITIAL

POPULATION) ( d )

NO

T E

LIG

IBL

E F

OR

LO

NG

ITU

DIN

AL

S

AM

PL

E

NO

LONGITUDINAL LINK

MA

TC

HE

D

LONGITUDINAL SAMPLE

NO

T M

AT

CH

ED

( h

)

LONGITUDINAL LINK

PRESENT IN THE LONGITUDINAL

SAMPLE

LONGITUDINAL WEIGHTS

MA

TC

HE

D

YES YES

NO NO

NO NO

NO NO

NO NO

NO NO

LONGITUDINAL SAMPLE

NO

T M

AT

CH

ED

( h

)

we don’t have enough information to distinguish not-respondents eligible from thise not-eligible.


Eligibility

All the individuals can be classified into two groups: Eligible:

– they represent part of the longitudinal population (because still living in the same municipality),

– they should be re-interviewed at the subsequent wave. – some of them are non-respondents in the final quarter, so that

they must be considered in a model for treatment of non-response (they must be represented by individuals with similar characteristics);

Not-eligible: – they left the initial population during the observed period

(deaths and migrations) – they do not represent part of the longitudinal population – they must be excluded from a model for treatment of non-

response.


Step 1 :

All the individuals which are linkable/matchable at the beginning of the period are selected.

are all the individuals of the two rotation groups which overlap at 12 month and resident in those municipalities which provided interviews for both waves;

they can be considered like a random sub-sample of the whole cross-sectional sample

their base longitudinal weights are obtained from cross-sectional weights applying the following correction

Weighting longitudinal data in three steps 1/3

PkkkLinkablei

iii 1* */


Step 2 :

•Accounts for bias due to municipality non-response

•Accounts for the differences between the rotation groups which overlaps and those who don’t;

•Help to ensure consistency between longitudinal and cross-sectional “official” estimates

the first calibration procedure makes matchable individuals at the beginning of the period

represent exactly the same cross-sectional population of the whole cross-sectional sample.

provide exactly the same cross sectional “official” estimates for a number of relevant figures (cross-classification of sex, region, age group, labour activity status, education, etc.).



Thus, from the base longitudinal weights and for all the linkable individuals the intermediate longitudinal weights

are obtained as result of a minimum constrained problem as follows:

rse

N

irsei

Linkableirsei Pwg 1

1,

*,

1

1

1

*N

iiii

Linkableii XwXg

),(min ***ii

Linkableii kkD

***iii kg



Step 3 :

•Adjusts for bias due to individual non-response

•Make weighted longitudinal-sample totals conform to the longitudinal population.

The hypothesis underlying is that

the non-response is random inside the cells resulting from nesting population by gender, by age groups and NUTS1, NUTS2 and NUTS3 domains



only for linked individuals the final longitudinal weights

are computed applying a new calibration stage to make weighted longitudinal component totals

conform to the longitudinal population under the following constraints

***iii kg

rsellinkedi

rsei Pw

*,

),(min ***ii

Linkedii ggD



Flow chart of weighting procedureStep 2

FIN

AL

CR

OS

S-S

EC

TIO

NA

LW

EIG

HT

S

CR

OS

S S

EC

TIO

NA

L S

AM

PL

E

AT

BE

GIN

NIN

G O

F T

HE

P

ER

IOD

PO

PU

LA

TIO

N I

N T

HE

IN

ITIA

L

QU

AR

TE

R

Internal MigrationInternational Mitration

Deaths

LONGITUDINAL POPULATION

INT

ER

ME

DIA

TE

LO

NG

ITU

DIN

AL

W

EIG

HT

S

MA

TC

HA

BL

E

SU

B-S

AM

PL

E


Flow chart of weighting procedureStep 3

INT

ER

ME

DIA

TE

WE

IGH

TS

FIN

AL

WE

IGH

TS

MA

TC

HA

BL

E S

UB

-SA

MP

LE

REFUSALSUNREACHABLE

Internal MigrationInternational Mitration

Deaths

RESPONDENTS

NO

T

MA

TC

HE

DM

AT

CH

ED




49

2

495

547

Deaths

Employed 20.346 353 1.281 21.980

Unemployed 489 449 514 1.452

Inactive 1.260 757 23.131 25.149

Total 22.095 1.559 24.926 48.581

Total

Labour Status at 2008Q1

InactiveLongitudinal Population Employed Unemployed

Lab

ou

r S

tatu

s at

20

07Q

1

Net change due to Longitudinal Population flows

+ 115

817

102

377

1.296

People Leaving theMunicipalities

22.846

1.556

26.021

50.424

Population aged 15+ 2007Q1

0 0 584 584 Children aged 15

1075 202 359 1.636 People Entering the Municipalities

23.170 1.761 25.870 50.801 Population aged 15+ 20087Q1

Net change in cross-sectional employment

+324

Net change due toMigratory flows

+ 258

Net change due to Demographic flows

- 49

Complete Matrix with net and gross flows. Quarter 1 2007 – Quarter 1 2008. (Thousands)


Transition Matrix for longitudinal population. Quarter 1 2007 – Quarter 1 2008. (Thousands)

Employed 20.346 353 1.281 21.980

Unemployed 489 449 514 1.452

Inactive 1.260 757 23.131 25.149

Total 22.095 1.559 24.926 48.581

Total

Labour Status at 2008Q1

Inactive

Longitudinal

Population Employed Unemployed

Lab

ou

r S

tatu

s at

20

07Q

1

Net change+105

Leaving employment

1.634

Entering employment

1.749

Persistence in employment

almost 3.400 movements


Main Findings

Potentials Longitudinal data provide extremely useful insights on labour

market dynamics Are obtained without important additional costs, but with high

investment in methodology Can be produced regularly on quarterly bases

Constraints EU-LFS is not a panel survey, thus longitudinal estimates can

refer only to a specific longitudinal reference population Known totals for this longitudinal reference population must be

available for weighting Methods for non-response treatment must be used to reduce bias Methods to ensure consistency with cross-sectional estimates

must be used


Some Examples of

Analysis of Labour Market

from Quarter 1 2004 – Quarter 1 2008

using 12 months longitudinal data


92,6

93,7

90,7

93,9

93,3

89,5

1,6

1,4

1,9

1,2

1,4

2,5

5,8

4,8

7,3

4,9

5,3

8

80 82 84 86 88 90 92 94 96 98 100

Italy

Male

Female

North

Center

South

Percentage Points

persistence in employment transition to unemployment transition to inactivity

Women have lower persistence probability and higher transition probability to inactivity

Employment: persistence and transition probabilities by gender and region. 2007Q1 – 2008Q1

South has lower persistence probability andmuch higher transition probability


79,8

84,6

90,5

94,7

74

94,2

92,6

6,5

5

2,2

1,2

2,2

0,9

1,6

13,7

10,4

7,3

4,2

23,7

4,9

5,8

70 75 80 85 90 95 100

Temporary - Employee - Part time

Temporary - Employee - Full time

Permanent - Employee - Part time

Permanent - Employee - Full time

Self Employed - Part time

Self Employed - Full time

Total employment

Percentage Points

persistence in employment transition to unemployment transition to inactivity

High segmentation in persistence and transition

Employment: persistence and transition probabilities by job characteristics. 2007Q1 – 2008Q1


Unemployment: transition probability to employment by duration of search at the starting point

20

25

30

35

40

45

2004Q1-2005Q1 2005Q1-2006Q1 2006Q1-2007Q1 2007Q1-2008Q1

Pe

rce

nta

ge

po

ints

Less than 6 months From 6 to 11 months 12 or more

Transition probability is inversely correlated to the duration of search for employment

Opportunities to get an Employment for long term Unemployed are stable in the period


30,9

34,6

27,3

24,4

26,2

35,9

33,7

36,9

30,6

45,8

37,8

25,9

35,4

28,5

42,1

29,8

36

38,2

0 10 20 30 40 50 60 70 80 90 100

Italy

Male

Female

North

Centre

South

Percentage Points

persistence in unemployment transition to employment transition to inactivity

Huge differences in the persistence and transition probabilities between North and South

Unemployment: persistence and transition probabilities by sex and NUTS1 region. 2007Q1 – 2008Q1

Higher probability to get an employment for men

Higher probability to leave labour force for women


THANK YOU

FOR YOUR ATTENTION

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