In longitudinal studies like the German Socio-Economic Panel (SOEP), which has been conducting comprehensive surveys with households across Germany since 1984, participants can choose to provide „no response“ to all questions (data set: SOEP-Core, v37, EU Edition). In the following, we examine the composition of those who chose „no response“ when asked about their voting decision in the 2017 federal election in the SOEP. The respondents had various options for indicating how they distributed their votes among the participating parties. In 2017, only 7.7% of the respondents did not provide an answer, making it difficult to derive statistically significant correlations. Cramér’s V measure showed no statistical significance for the observed irregularities in the calculation. However, examining the composition of the group still yields interesting insights.
For both years, respondents could indicate whether they did not vote (if eligible), which party or parties they voted for, or whether they wanted to provide „no response.“ Invalid votes or invalid responses within the survey were excluded from this analysis.
In the 2017 federal election, the group that chose „no response“ consisted of 1,859 individuals, while 19,853 respondents indicated their voting decision. This means that the overall ratio was 92.3% responded, 7.7% did not. I was particularly interested in how these numbers differed when we look at gender, education level, interest in politics, poverty status, and income. The following analysis takes into account the size of the groups, i.e., whether, for example, more men or women were surveyed, as it proportionally represents the response behaviour.
Women (gender is measured as binary in the SOEP) more often chose „no response“ (8.3%) than men (7.1%). Respondents with a secondary school degree (Realschulabschluss), considered as „intermediate education level,“ particularly frequently refused to provide an answer. Interestingly, respondents with a lower secondary school degree (Hauptschulabschluss) or no degree disclosed their voting participation at the same rate as the highly educated group.
6.9% of those living below the poverty line refused to answer, while the proportion was 7.8% among those who were not poor. This result shows that the economically disadvantaged in this analysis were more likely to provide answers compared to those with household incomes (weighted) above the poverty line.
The higher the level of political interest, the higher the proportion of respondents who answered. While „no“ or „not much“ interest leads to refusal rates of 9.4% and 9.1%, respectively, it decreases to 6.1% for strong interest and 4.8% for very strong interest – the lowest refusal rate observed here. Thus, political interest appears to play a significant role in the decision of whether respondents provide their voting decision.
To represent the income distribution of all respondents and divided into provided or withheld responses, I first calculated income deciles. This divides the group of respondents into ten equal-sized groups. The lowest 10% represents those with the lowest income, the second decile includes respondents who have between 10% and 20% of the income distribution, and so on. This makes the data more robust against outliers due to particularly low or high incomes. The following graphic shows how incomes are distributed within each group proportionally.
The graphic shows the „kernel density estimators,“ i.e., the probability that a respondent has the displayed income if they belong to the respective group. Individuals who provided „no response“ (yellow line) have a higher probability of having incomes in the lower range of up to 1,500 euros per month.
The median income for the entire group of respondents is 1,666.67 euros, for those who provided responses it is 1,736.67 euros, and for those who withheld responses, it is 1,700 euros.