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For more than three decades, declining response rates have been of concern to both survey methodologists and practitioners. Still, international comparative studies have been scarce. In one of the first international trend analyses for the period 1980–1997, De Leeuw and De Heer (2002) describe that response rates declined over the years and that countries differed in response rates and nonresponse trends. In this article, we continued where De Leeuw and De Heer (2002) stopped, and present trend data for the next period 1998–2015 from National Statistical Institutes. When we looked at trends over time in this new data set, we found that response rates are still declining over the years. Furthermore, nonresponse trends do differ over countries, but not over surveys. Some countries show a steeper decline in response than others, but all types of surveys show the same downward trend. The differences in (non)response trends over countries can be partly explained by differences in survey design between the countries. Finally, for some countries cost indicators were available, these showed that costs increased over the years and are negatively correlated with noncontact rates.

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.