‘Unsatisfactory Saturation’: a critical exploration of the notion of saturated sample sizes in qualitative research

Measuring quality in qualitative research is a contentious issue with diverse opinions and various frameworks available within the evidence base. One important and somewhat neglected argument within this field relates to the increasingly ubiquitous discourse of data saturation. While originally developed within grounded theory, theoretical saturation, and later termed data/thematic saturation for other qualitative methods, the meaning has evolved and become transformed. Problematically this temporal drift has been treated as unproblematic and saturation as a marker for sampling adequacy is becoming increasingly accepted and expected. In this article we challenge the unquestioned acceptance of the concept of saturation and consider its plausibility and transferability across all qualitative approaches. By considering issues of transparency and epistemology we argue that adopting saturation as a generic quality marker is inappropriate. The aim of this article is to highlight the pertinent issues and encourage the research community to engage with and contribute to this important area.