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In an optimal design for mixed‐mode surveys, be it within a country or across countries, there are three phases that need attention. The first phase is the design phase: it is important to prevent mode measurement effects when designing the study. A richer source of additional data will help to achieve a better estimation of mode effects. After the data are collected, the next two phases are estimating the potential mode measurement effect due to different modes and adjusting for any such bias. Survey modes differ on several dimensions, for instance, interviewer‐administered versus self‐administered questionnaires and information transmission and communication. The use of well‐established and validated constructs and multiquestion scales across countries and modes helps achieving measurement equivalence countries and modes. Mixed‐mode designs and mode changes are often implemented for sound methodological reasons. Using a mixed‐mode design implies a careful trade‐off among coverage, nonresponse, measurement errors, and cost.

Household survey nonresponse is a matter of concern in many countries. In one of the first international trend analyses, de Leeuw and de Heer (2002) found that response rates declined over the years, and that countries differed in response rates and nonresponse trends. Their analyses cover longitudinal data on the Labour Force Survey from National Statistical Institutes for the period 1980 to 1997. We added a new data set, covering the period 1998 -2015, and analysed nonresponse data over time and countries. In these analyses we differentiated between voluntary and mandatory surveys. The trends visible in de Leeuw and de Heer (2002) continue with possibly a small deceleration in refusal rates.