BCS70 Age 30 Sweep

Sweep details

Dates November 1999 – September 2000
Age 29-30
Achieved sample 11,261 (cohort members)
Respondents Cohort members
Fieldwork agency NatCen Social Research
Survey mode Face to face
Data access

Main dataset available via the UK Data Service [SN 5558]. Visit the UK Data Service website to access the data.


The Age 30 Sweep involved a 60-minute interview covering: relationships, births and pregnancies, lone parenthood, children, family life, housing, employment, income, qualifications and training, computer use, basic skills, physical and mental health, diet and exercise, alcohol consumption, smoking, illegal drug use, height and weight, social participation, voting, attitudes, contact with the police.

The Age 30 Sweep was conducted in tandem with the Age 42 Sweep of the 1958 National Child Development Study. Over 90% of the questions asked were common to both surveys.

Special features at age 30


For the first time, cohort members provided information about their family income beyond individual earnings.

Earnings from employment were collected at age 26, but the Age 30 Sweep was the first time that BCS70 sought to collect a fully comprehensive measure of all sources of family income. Income has been a significant feature of all subsequent surveys, allowing for the study of income mobility and the inter-relationship between income and other aspects of life.

Computers and the internet

Questions about internet usage were first asked at age 30 and have been included in BCS70 sweeps ever since.

The cohort has experienced extraordinary levels of technological change across many domains. As teenagers, they listened to electropop cassettes on their Sony Walkmen. They taped the first episodes of Eastenders on their brand new video recorders. However, the most notable change has been the revolution in computing and IT. Home computers came into the mainstream in the early 80s. The ZX Spectrum computer came onto the market in 1982, and many of the boys (but fewer girls) of the 1970 cohort would have owned one of these inexpensive machines, which were mostly used for games. BCS70 cohort members would have used pen-and-paper for all their schoolwork and for their university essays in the early 1990s. However, the majority would start to use computers in the workplace and at home in their 20s and 30s. The internet became hugely important commercially with the dotcom boom of the late 90s.

Relationships, housing and employment histories

Cohort members listed all cohabiting relationships, periods of economic activity and housing since age 16.

These ‘histories’ have been continually updated in every subsequent survey and can be used to study the trajectories which people follow through life and how transitions in different domains of life are inter-related.


  • User guides
  • Questionnaires
  • Technical reports
  • Data notes
  • Additional
User guides

Handling missing data in the CLS cohort studies – User Guide

This user guide aims to describe and illustrate a straightforward approach to missing data handling, while detailing some more general considerations around missing data along the way.

Date published: 03/06/2024
PDF: 1000,62 KB


NCDS6/BCS 2000- Guide to the Combined Dataset

Date published: 01/06/2001
PDF: 1,2 MB


BCS70 Partnership Histories (1986-2013) Guide

Date published: 01/10/2016
PDF: 370,43 KB


BCS70 Activity Histories (1986-2013) Guide

Date published: 01/07/2017
PDF: 660,51 KB


NCDS Age 42 / BCS70 Age 30 Questionnaire

Questionnaire for cohort members administered for the NCDS age 42 and BCS70 Age 30 sweeps.

Date published: 01/12/2002
PDF: 3,15 MB


NCDS Age 42 / BCS70 Age 30 Questionnaire Appendices

Date published: 01/12/2002
PDF: 1,47 MB

Technical reports

NCDS Age 42 / BCS70 Age 30 Technical Report

Technical report on the NCDS age 42 and BCS70 Age 30 sweeps.

Date published: 01/09/2001
PDF: 1,21 MB


NCDS Age 42 / BCS70 Age 30 Technical Report: Appendices

Appendices for the technical report on the NCDS age 42 and BCS70 Age 30 sweeps.

Date published: 01/09/2001
PDF: 2,24 MB

Data notes

NCDS Age 42 and BCS70 Age 30 Data Note 2: Pregnancy Histories

Assessment of combined pregnancy histories of BCS and NCDS when both surveys were conducted between 1999/2000

Date published: 01/12/2002
PDF: 436,93 KB


NCDS Age 42 and BCS70 Age 30 Data Note 3: Household Grid Variables

Assessment of combined household grid variables of BCS and NCDS when both surveys were conducted between 1999/2000

Date published: 01/12/2002
PDF: 592,55 KB


Deriving highest qualification in NCDS and BCS70

This Data Note explains the derivation of variables on Highest Educational Qualification obtained by cohort members in the National Child Development Study (NCDS) and the 1970 British Cohort Study (BCS70).

Date published: 01/01/2011
PDF: 514,11 KB


BCS70 age 30 – questionnaire routing

Date published: 01/01/1999
PDF: 431,34 KB


BCS70 age 30 – questionnaire introduction

Date published: 01/01/1999
PDF: 427,72 KB


BCS70 Revised Region Variables (Third Edition)

This User Guide accompanies the deposits at the UK Data Archive of derived variables for each sweep of BCS70. These derived variable datasets are found under the study number for each of the sweeps and include variables for country of interview, region and government office regions.

Date published: 01/02/2014
PDF: 307,78 KB


BCS70 Ethical Review and Consent

Review of Ethical procedures used for each Sweep of BCS70.

Date published: 01/01/2019
PDF: 4,18 MB

Contact us

Centre for Longitudinal Studies
UCL Social Research Institute

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London WC1H 0AL

Email: clsdata@ucl.ac.uk

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