Modelo de consumo para análisis Big Data y clasificación de conductores

Dividing the samples

In the BHPS, information on respondent’s lifetime partnership histories was collected in wave two (1992) for all respondents and then again in waves eleven (2001) and twelve (2002) for those entering via the Scotland and Wales extension samples and the

Northern Ireland extension sample respectively. These data are contained in the record files wCOHABIT and wMARRIAG. In addition, in wave eight a small number of

13 _{It is acknowledged that the inclusion of Temporary Sample Members (TSMs) in the sample could have} implications for the subsequent analyses given that their exit from the sample might be related to them having the event (i.e. repartnering). In fact, less than 3% of the final sample (15 cases) were TSMs and therefore this is unlikely to represent a problem for this study.

variables were included in the individual questionnaire (HINDRESP) to collect ‘catch up’ information on start and end dates for previous cohabitations, the number of

marriages and the date of first marriage for any respondents that were not interviewed in waves one or two or were a new entrant over 16 years of age and had lived with

someone as a couple at some point or ever married. A number of these variables, including the start and end dates of a respondent’s first cohabitation, the date if a partnership of this type had occurred, the number of marriages and dates of the first of these if applicable were also collected in subsequent waves for those not interviewed before. Due to this information being collected at these different time points for the different groups of lone mothers, all those lone mothers who were part of the ECHP or Wales, Scotland or Northern Ireland extensions samples were selected out of each of the original twelve samples to create another six samples in order for their partnership histories to be created separately.

The process of obtaining data to observe their partnership histories

For the first of the twelve samples, which included the original Essex sample of women that entered lone motherhood in the second wave of the BHPS in 1992, the coding of their most recent previous partnership and total number of previous partnerships was a straightforward process due to the collection of the retrospective marital and

cohabitational histories at this wave. This information was simply merged into the sample with the use of the personal identification variable with the coding of the start and end dates of their most recent partnership and the number of total partnerships carried out as described below. The same process was carried out for those in the extra sub-samples that entered lone motherhood in 2001 when the retrospective marital and cohabitational histories were collected again.

However, for subsequent samples including all lone mothers entering lone motherhood at some point after 1992 and those in the extra sub-samples entering lone motherhood before 1997 or after 2001 it was necessary to look back at their responses to certain variables from each wave prior to them entering lone motherhood. These variables included those relating to their marital status, whether their spouse was living in the household and the spouse’s personal identification number at each time point. The beginning of the previous partnership was then identified in the same way that the lone mothers were identified initially, by comparing two waves and observing a marital status change between these two time points. Although in general it was assumed, and

in fact appeared to be the case, that women only made one marital status transition in each event period, it is possible that a woman may be recorded as being married in two successive waves, but in fact an intervening divorce and subsequent re-marriage has occurred (Peters, 1988). In this circumstance the spousal identification numbers would be different for each marriage. Therefore close attention was paid to the personal identification number of the spouse as well as whether the spouse was living in the household at each time period in order to detect such transitions. In some cases where the previous partnership was relatively long in duration it was necessary to use the retrospective partnership histories in addition to the above procedure to determine the beginning of the previous partnership. For all these samples the partnership history data was used as well, where present, in order to identify number of previous partnerships. Finally, for a number of previously partnered women it was possible to obtain

information on partnership history using the ‘catch up’ marital and cohabitation history collected in wave eight and the responses to the small number of partnership history variables collected in subsequent waves as described above.

Defining previous partnership duration

In each case, no matter whether it was necessary to use the retrospective history data or just to examine the responses from previous waves to determine the length and number of previous partnerships, the beginning of a previous partnership was defined as the point at which the couple either began a cohabitation (even for those who subsequently married) or at the time of marriage for those who did not cohabit pre-maritally. Due to the fact that many of the most recent previous partnerships of these lone mothers began after 1992 and only detailed information on the exact month of a change in legal marital status14 is collected annually, it was not possible to determine the month in which the most recent previous partnership began for the majority of the women becoming lone mothers through the breakdown of a cohabiting union. As previously highlighted above it was also impossible to determine the exact month in which the partnership ended resulting in them becoming a lone mother. The duration of the most recent previous union was therefore determined in terms of years by subtracting the year in which it began from the year in which it ended (with the year it began being taken either from the lifetime history data or referring to the survey year in which they were first observed to be in that partnership). Since the variable measuring the duration of the prior union

14

A change in legal marital status refers to those who made transitions between married, divorced or widowed states and does not detect transitions into or out of a cohabiting union.

in the analysis is to be grouped and the substantive interest is in whether those with long durations (e.g. 10 years) have significantly different repartnering patterns compared with those who had much shorter durations of only a couple of years, then not being able to measure union duration more accurately in terms of months, rather than years, is unlikely to make a significant difference in the analysis.

Defining the number of previous partnerships

In order to identify the total number of previous partnerships a lone mother had had, it was necessary that lifetime cohabitation or marital history was collected at some point across the survey waves for an individual. If entry into lone motherhood occurred after this time it was necessary that they had been observed in each wave subsequent to the collection of the histories and up to the time of becoming a lone mother, unless there was evidence to suggest their partnership status had not changed over any years they were missing from (see section on wave non-response and the coding of partnership status below). In general, information on total number of previous partnerships was obtained from the lifetime cohabitation and marital history data collected in wave two of the BHPS. However, for a number of women who were not interviewed at this time (mainly due to the fact they were either a TSM and hence not present in the survey at this time, or because they were a child under age 16 years) it was possible to obtain this information from the ‘catch up’ cohabitation history information collected in wave eight. In addition, the limited variables on partnership history collected in waves subsequent to wave eight also allowed the identification of the number of previous partnerships for some women.

In some circumstances it was not possible to identify the total number of previous partnerships of a lone mother due to missing marital or cohabitation history data; high levels of wave non-response in preceding years up to entry into lone motherhood; or other reasons such as missing information on the personal identification number of the spouse or inconsistencies between the individual and marital or cohabitational history files. In such cases, the total number of previous partnerships was recorded as missing (see Section 4.5.3 on item non-response for a discussion of the numbers involved and the method implemented to deal with this missing data).

In addition to this, if a woman recorded herself to be never-married in between two years where she is reported to be in a cohabitation with the same person, then the

partnerships either side of the year(s) of being never-married were coded as two

separate partnerships (this only concerned three women overall). In the same respect, if a woman went from being in a partnership with one person in one year, then was in a partnership with another person in the following year, but then went back to the original partnership a year later, the partnerships were coded as three separate partnerships (this only actually concerned one woman). These decisions were due to the fact that the aim of this variable was to distinguish between those people that remained in a stable partnership for a long period of time versus those that moved in and out of a

partnership. Whether or not it was with the same person was not of particular interest.

Wave non-response and the coding of partnership status

Considering wave non-response it was decided that any women with missing information over a period of one or even several years due to the fact that they were unable or refused to be contacted were assumed to have remained in the same

relationship with no break if they were found to be either cohabiting or married with the same partner either side of the missing year(s). Since the personal identification number of the spouse was measured in each wave then identifying whether the partner was in fact the same person in each wave surrounding the missing year(s) was straightforward. Where a woman was missing and a different partnership was observed either side of the missing year(s) and this concerned the most recent previous partnership, the duration of the partnership was set to missing.

Inconsistencies between the marital and cohabitation history data and data

collected in the individual file

In coding the partnership histories of these lone mothers it became apparent that there were some inconsistencies between the information collected in the individual file on marital status and that collected in the cohabitation or marital history files for a small minority of cases. In each of the four cases the respondent was reported to be either never-married or separated in wave two (1992) according to the individual file, but according to the history file was recorded as cohabiting at this time. For two of these women this had no effect on the coding of their previous partnership duration as they actually only entered lone motherhood in 2002 and hence the inconsistency was related to a different partnership previous to the one which resulted in them becoming a lone mother in 2002. However, for the remaining two cases this inconsistency was related to their most recent partnership with the individual file recording both these woman to be

never-married in 1991 and 1992 and cohabiting in 1993, but the cohabitation history file collected in 1992 reporting both woman as cohabiting at this time with cohabitations beginning in 1991 and 1992 respectively. Since it was unclear whether in fact the relationship recorded in the history file in 1992 was the same relationship as that recorded in the individual file a year later and also if it was, when exactly it began, it was decided to use the information collected in the individual file as being correct (for a more detailed explanation of the reasoning for this decision see Section 4.5.4 where recall bias is discussed). This meant that their previous partnerships were coded as beginning in 1993 for both women and hence their previous union duration was measured as two years and one year less respectively, compared to if the information from the history file had been used. Since, as previously mentioned, the variable measuring previous union duration is to be grouped in the analysis this slight discrepancy is unlikely to affect the analysis in any case. The discrepancy was also taken into consideration when coding the total number of partnerships a woman had previously had. Since it was not certain whether this was a different partnership or not then it was not included as so.

Another discrepancy between files concerned one woman who was recorded in the individual file in 1992 as separated from a marriage, yet when matching the responses for this women from the marital history file no information was found relating to the starting and separation dates of this relationship. Interestingly though, it was found that there were some partnership start and end dates recorded for this woman in the

cohabitation history file. Since the end dates found in this file matched with the information found in the individual file for this woman it was assumed that this was an error made by the interviewer whereby the dates of the separation of the marriage were filled out on the form relating to cohabitations instead. These dates were therefore substituted as the dates of separation of the marriage in the absence of any other information.

4.3.3 Coding of partnership histories for those entering lone motherhood through