Longitudinal customer research

Longitudinal customer research can help drinking water utilities better tailor their services to their customers. To enable the best possible design of these studies, an ‘ideal’ questionnaire has been developed, as a part of a larger whole. To this end, the questionnaire’s parameters have been outlined, based on the analyses of other questionnaires, the international literature and on interviews with experts. The optimal questionnaire also offers the possibility of studying whether and how customer perspectives change over time. With these insights, drinking water utilities can better tailor their services to specific customer groups.

Longitudinal studies enhance a nuanced understanding

It is more valuable to study the same drinking water customers at numerous moments over time, than to have different snapshots among different drinking water customers. This is because the same observations made over a longer period signal changes more easily.  This is what is known as longitudinal research. It is important that this research be conducted well and consistently. Longitudinal customer studies help achieve a nuanced understanding of the attitudes and perception of the customer regarding risks, water awareness, alternative water sources, sustainability aspects, and drinking water rates. Longitudinal studies can also provide information about the evolution of customer perspectives over time, which allows drinking water utilities to better understand their customers and to better tailor their services to them.

Designing an ideal questionnaire

In this research project an analysis was carried out of the international literature on longitudinal research. What for instance do you need to pay attention to when designing such research? And how does this differ when compared to cross-sectional research? Cross-sectional studies only observe the measured change, and can therefore produce measurements that are disconnected from actual change. Longitudinal research measures the actual change over time, which results in more optimal observations.

To discover the extent to which KWR’s current customer research takes cohesion, or the longitudinal aspect, into account, 27 questionnaires from 8 different projects were analysed in terms of the coherence of their structure, context, themes and response. In addition, eight interviews were conducted with experts in longitudinal research, KWR customer research, and water-sector developments. This led to the identification of methodological parameters. For example, in the conduct of longitudinal studies attention needs to be paid to the number of participants, costs, means required, research duration, validity, ethics, data, pilot studies, wording of questions, and external influences. On the basis of this knowledge, an ideal questionnaire for longitudinal customer research was developed.

Better respond to specific customer groups and their needs

Until the time that the longitudinal research is actually carried out in KWR’s customer research, the ideal questionnaire provides a good starting point for tackling this method in existing and new projects with consistency. Among other things, the questionnaire offers the opportunity of studying whether and how customer perspectives change over time. With these insights, drinking water utilities can better tailor their services to specific customer groups, thus improving the success factor. In addition, the analysis of longitudinal research presents a range of possibilities: the clarification of water-use patterns, the identification of water-demand trends, the evaluation of the impact of water-conservation initiatives, and assistance in developing more accurate projections of future water needs.

Actual change (a) versus measured change (b). Longitudinal studies continue where cross-sectional studies stop.