The extent of demographic diversity in some migrant‐receiving countries has led to the formation of majority‐minority (or superdiverse) cities, a phenomenon also found in New Zealand. Recognising that demographic diversity is dynamic, sensitive to mobility patterns and shifts in socioeconomic indicators, this study examines diversity through the lens of common (nonofficial) languages (n = 21), by employing customised census data spanning five consecutive census years (1996–2018) that provides insights into ethnicity, religion, education, employment, income, and residential density. Considerable variation was found in the identification with one or more religious and ethnic attributes; while some language speaker groups (LSGs) displayed a strong, stable identification, other cases were characterised by fluctuations and mobility. Similarly, considerable differences between LSGs were found with respect to education, employment and income, which can partially be explained by selective migration. Finally, residential density has increased in secondary cities, particularly among LSGs with more dynamic socioeconomic indicators. The analysis, informed by the different migration histories and settlement experiences of the LSGs, contributes to understanding the dynamic quality of diversity indicators and the relative socioeconomic im/mobility of some groups, and demonstrates how the concepts of superdiversity and hyper‐selectivity can be operationalised.