Health Survey as of 2014

What does the survey comprise?

Purpose

To provide the most complete picture possible of developments in the health, medical contacts, lifestyle and preventive behaviour of the Dutch population.

Survey population

For the majority of topics, persons aged 0 years and over living in private households. For some topics, other age limits apply.

Statistical unit

Persons.

Year survey started

Statistics Netherlands has been conducting an annual Health Survey since 1981. In the period 1997-2009, the Health Survey was part of the Continuing Survey on Living Conditions (POLS). As of 2010, the Health Survey is being conducted as an independent survey again.
Information on previous editions of the Health Survey (2010-2013) can be found here: Health Survey, 2010-2013

Frequency

Annual.

Publication strategy

The figures are definitive.

How is the survey conducted?

Sampling technique

A representative sample of persons is selected from the Personal Records Database (BRP). Sampling is distributed evenly over all months of the year.

Observation method

As of 2014, the Health Survey is conducted in the so-called ‘mixed mode’ setup. Sample units from the population are asked to participate via the internet (CAWI – Computer-Assisted Web Interviewing). Non-respondents are reapproached to participate in a face-to-face interview by way of Computer-Assisted Personal Interviewing (CAPI).
As of 2018, a new target group strategy is being adopted. This means that not all reapproachable CAWI non-respondents are actually reapproached for a CAPI interview. In cases where a particular target population has yielded a relatively high response rate in CAWI, a smaller sample of this target population is being reapproached for CAPI. In this way, the CAPI mode is used more selectively with special focus on the groups with low CAWI response rates. The final total response will thus better reflect the total population. The target groups have been determined based on the background characteristics on which information was available during sampling. Examples of background characteristics include age, income and migration background.

In addition, incentives have been introduced with effect from 2018. This means that respondents have a chance to win a prize. This is described in the invitation letter.

The questionnaire contains questions of a personal nature, CAPI respondents are given the opportunity to complete those parts of the questionnaire by themselves (CASI – computer-assisted self-interviewing).

Respondents

Persons living in private households. For respondents under the age of 12, the survey questions are answered by a parent or caretaker.

Sample size

Every year, a gross sample of over 15 thousand people is approached. For the years 2014-2017 the response rate was 60-65 percent. As of 2018, a target group approach has been introduced (see 'observation method'). By definition, this has resulted in lower response rates as a relatively smaller part of the CAWI non-response is being reapproached for a CAPI interview. On the other hand, the incentives - also introduced in 2018 - have boosted response rates. Overall, the total response rate is approximately 60 percent as of 2018. The net sample (i.e. the final number of respondents) stands at approximately 9,500 persons per year.

Checking and correction methods

Every year this sample survey is checked for plausible results, internal consistency and completeness.

Weighting

To correct for differences between the composition of the net sample and the total population, a weighting factor is applied based on the following characteristics: gender, age, migration background, marital status, urban environment, province, province, household size, income, wealth, and survey season, and as of 2018, target group.

What is the quality of the results?

Accuracy

The health survey entails a sample, so the figures are subject to chance fluctuations. Standard margins can be used to determine reliability margins around the figures. The lower and upper limits of the 95% confidence interval are shown in the StatLine tables. The 95% confidence interval around the mean ranges from 'mean minus 1.96 * standard error' to ‘mean plus 1.96 * standard error'.
If the number of respondents for a given classification category is less than 100, no results are presented due to oversized margins.

Comparibility over the years

Some caution should be taken into account when comparing results as from 2014 with results over the period up to and including 2013. Between 2013 and 2014, several significant changes were introduced in the Health Survey.
Up to and including 2013, the survey consisted of two research components: the first part of the questionnaire allowed respondents to complete the survey via the internet, telephone or personal interview. The second part of the questionnaire always had to be done via the internet or on paper.
However, as of 2014 the survey has consisted of only one part. Respondents can only complete the entire questionnaire via the internet or personal interview. In addition, changes were made to the structure and composition of the questionnaire from 2014 onwards, and in some cases there have been changes to the question semantics. Furthermore, the weighting of the Health Survey has been modified.

The changes between 2013 and 2014 led to a number of method contraventions, as shown by a method breakdown analysis. More information on this analysis and the established method breaks can be found here in Dutch: Methodebreuk Gezondheidsenquête 2014.