Despite recent electoral gains in some national elections, almost all social democratic parties in Western and Northern Europe have lost a significant amount of their vote share in past decades. Some of those parties, such as the Dutch PvdA or the French PS, struggle to reach double-digit vote shares.
These electoral losses are even more pronounced when focusing on specific age groups: Even in the 2021 German Federal Elections, where the social democratic SPD could gain votes and managed to come out as the strongest German party, exit polls displayed strong age differences in their support base: The vote share among the youngest age group 15% among German voters aged 18 to 2 was 20 percentage points lower compared to voters older than 70. Figure 1 reveals that the considerably large age differences within the German social democratic electorate have become even more distinct over the past elections. Having said this, the situation in Germany is similar to the one in other Western European countries. Moreover, similar patterns seem to be visible for other (former) social democratic strongholds, such as Sweden, where the SAPs vote share in recent polls has been twice as high among the oldest voters compared to the youngest voters.
Figure 1.- SPD vote share among age group
In stark contrast to this, other parties from the (center-)left have been able to gain electoral success both among the whole electorate and among the youngest voters: In the 2021 Federal Elections, the German Greens could further expand their vote share among newly eligible voters.
The party became together with the liberal FDP the strongest party among the 18-24 years old voters (23% voted for the Greens). Figure 2 shows the age support differences for the German Greens over the last 20 years: Interestingly, while the party could particularly increase its support among young voters, they gained votes among all age groups with people over 60 still showing the lowest levels of support.
Figure 2.- Bündnis 90/Die Grünen vote share among age groups
Again, it is necessary to stress that this green electoral success is not a German story: In other Western and Northern European countries, green and other alternative left parties have also gained a considerable number of votes. In Finland, Switzerland, Belgium, the Netherlands, or Austria, green-alternative parties could all expand their vote share and have become as strong or even stronger as social democratic parties among young voters. Altogether, there seems to be a substantial age-vote-divide on the political left in 21st century Western Europe: Older leftist voters prefer social democratic parties, while their younger counterparts seem to rather vote for the green(er) alternative.
Life-Cycle vs. Cohort Differences
Having said this, these developments do not necessarily have to worry social democratic parties in the first place. Having an old electorate does not ultimately have to be something bad for a party, particularly when looking at potential electoral benefits: As various research has repeatedly shown, older voters do turn out to vote more regularly and more frequently than their younger counterparts. Furthermore, Europe experiences a steady greying of its societies. With increasing life expectancy and declining fertility rates, Europes populations are strikingly aging and will potentially further continue to do so. It is thus most likely that the political leverage of older voters will be steadily increasing in the upcoming decades. When voting behavior proves to be volatile over a voters life and voters might thus be expected to switch to vote for a specific party when getting older, social democratic parties seem to be in an electorally rather comfortable position. According to this idea of voting that follows the life-cycle of a person, citizens are thought to adapt their political behavior when aging. If those assumptions would hold, social democracys electoral future might look rather bright despite low levels of support among young voters throughout Europe. In other words, becoming a pensioners party could even be considered to be an electorally successful strategy and might be a potential explanation for the electoral triumph of Olaf Scholz in 2021.
However, this explanation underestimates the stability of political attitudes and behavioral habits, once they have been formed. In particular, explanations that assume age-based volatility in voting behavior undermine the importance of political socialization processes which take place in voters formative years. Those processes are crucial in fostering political identities among voters coming of age. Thus, once adolescent voters have formed their political identity, they often stick to their core values and attitudes, their party identification, and behave alike. While these 'cohort approaches' do not expect voters behavior to be completely stable after their formative years, they assume that there is a considerable degree of persistence in political attitudes and behavior. Accordingly, once voters have been politically socialized, they are rather unlikely to fundamentally change their political stances and party identification.
From a party perspective, it should thus be particularly important to address upcoming emerging generations to persistently gain future loyal voters. This is especially important, as voters in their so-called impressionable or formative years are significantly more receptive to political influences. Having an old electorate, therefore, raises the probability that this over-aging leads to a shrinking vote share in the mid-and predominantly in a long-term perspective. For social democratic parties, this means that the most recent short-term electoral gains might be deceptive: With generational replacement in place, social democratic parties might rather fear that their electoral struggle is likely to further unfold in the future, as formerly loyal voters die and no younger voters in similar numbers seem to be socialized with these parties. Rejuvenating the electorate may thus be an important factor for long-term electoral success.
Cohort Differences in Salience
Given this, at least two questions desire to be answered: First, why might we be seeing those age differences on the political left? Second, how likely is it that these voting differences of age groups persist over time?
Turning to the first question, there is evidence that those differences are reflecting a diverging perception of dimensional salience within the (potential) left electorate. Seminal work on value change from Inglehart, Dalton, Kitschelt, and Graaf and Evans has already early on demonstrated that newly emerged cohorts of voters are attaching a higher salience on issues that can be best located on the second dimension of politics. Most famously, Ronald Inglehart has repeatedly shown evidence for an occurred "postmaterialist value change" in post- industrial and "postmodern" societies. Furthermore, the mentioned studies have also pointed at new forms of mobilization (protests, outer-parliamentary demands that had been brought on the agenda) that may lead younger generations to prefer left alternatives over the social democrats. Thus, the (often) ambiguous way how green parties in Western Europe have managed to push new political demands on the political agenda has especially influenced voters coming of age during those years.
More recent research relying both on observational data and experimental data also shows that the electoral appeal of social democratic parties that propose more progressive stances on the socio-cultural dimension is strikingly higher among younger voters. According to this, the probability to vote for a more progressive social democratic party is around 15 percentage points higher for voters in their 20s. Hence, the second-dimension position that left parties takes, distinctively matters for young leftist voters electoral behavior.
In sum, this points to the fact that younger voters on the political left are attaching a diverging salience to different issues or even different dimensions altogether when compared to older social democratic voters. This is supported by other findings: Younger cohorts in Western Europe do perceive issues from the socio-cultural dimension to be more important than socio-economic issues. Among these cohorts, immigration issues and questions revolving around environmental protection are also more strongly associated with left-right self-positioning or party preference than for older voters. Therefore, young voters who attach greater importance to issues such as climate change, immigration, or gender equality are more likely to vote for a party that is more closely attributed with progressive stances on this dimension.
Green and alternative-left parties, who had been campaigning on these issues for quite a long time, are perceived as the more ambiguous and more credible alternative on the political left. Since their emergence, greens have developed into rainbow catch-all parties representing several new socio-cultural demands that have entered the political agenda. Young leftist voters who place a higher salience on those topics and this political dimension altogether, may thus rather vote for Green than for social democratic parties even when these parties may be ideologically close to each other. Taken together, age differences within the electoral structure of the left seem to represent differences in the importance that voters attach to certain issues or dimensions altogether. Young leftist voters prefer these parties that are more strongly perceived to represent a progressive position on second-dimension issues, while older voters prefer those parties that are more strongly connected to issues regarding the economic- political dimension.
The 'greying' of social democracy
However, the question remains whether this represents a rather short-term phenomenon, or if these differences are likely to persist over time. If the latter would be the case, it would be more meaningful not to speak of age (or life-cycle), but rather of generational differences: According to this, age differences do not reflect differences in a voters life cycle but generationally shared differences of political attitudes, salience, and finally party preference. Thus, voters aging together and belonging to the same birth cohort may be expected to stick to their positions and the relative importance they attach to specific political dimensions.
Surely, it is not yet possible to tell whether the most recent age differences will persist and thus further contribute to a shrinking vote share of social democratic parties. It is possible, however, to focus on earlier evidence regarding the persistence of political attitudes and vote behavior more specifically. Looking at longitudinal data, these assumptions seem to hold empirically. When observing birth cohorts for a longer period, it becomes evident that diverging salience seems to be rather resilient once manifested.
Furthermore, more recent analyses demonstrate that there are significant age differences on the left when it comes to progressive issues with voters older than 60 being less likely to choose social democratic programs than younger voters. This hints at fundamentally divergent perceptions when it comes to the salience that different age groups attach to political dimensions.
To control whether we see the consistency of these effects, I analyzed data from the European Values Survey and the World Values Study for seven Western European countries (Austria, Belgium, Finland, Germany, Netherlands, Switzerland, Sweden) and applied methods to distinguish the different dimensions of age. Doing this shows that generational vote differences on the political left can be empirically proven: Voters socialized in the 1980s and later on are more likely to vote for a green party. Voters born and socialized in earlier times had been more likely to vote for a social democratic party. Accordingly, one might conclude that this rather precisely mirrors the emergence of both new issues, as well as the green parties that ambiguously promoted these new topics.
Figure 3.- Probability of voting for greens vs. social democrats by year of birth
For social democratic parties, this is rather bad news. Turning back to Germany, the most recent electoral success of the SPD may thus need to be put into perspective. While the SPD was able to bring the electoral downtrend to a short-term halt, it is at least questionable if the party will be able to reverse this trend from a mid- or long-term perspective. Looking at voter flows data from exit polls, it was estimated that the SPD had lost more voters in relative numbers that had died in the last four years than any other party in Germany. Adding a long-term perspective further underlines this point. While the SPDs relative vote share among people older than 60 has remained rather stable over the past 20 years, the partys vote share among younger generations has dramatically declined.
It is important to stress that this has not always been the case: Back in the 1970s and 10 years before the Green Party appeared as a viable alternative on the ballot, the SPD got around 50% of the vote share among newly eligible voters. Furthermore, the SPD has also been struggling to rejuvenate its membership base in past decades: In the 1970s, members younger than 30 had made up around a quarter of the SPD members, while in 2020, only 8% percent were younger than 30. In contrast, more than 55% of SPD members were older than 60 years in 2020.
Facing these demographic shifts, social democratic parties thus need to develop ways to better reach out to young voters. Firstly, one possibility might be to achieve this with better (descriptive) representation: It has been shown even if the effect sizes may be rather small that young voters prefer to vote for young politicians. Regarding this, the Federal Elections 2021 in Germany might serve as a glimmer of hope: The newly elected SPD MPs are significantly younger than their social democratic predecessors. Secondly, it may be even more important for social democratic parties to more strongly, more credibly, and more ambiguously address socially progressive issues: In times of a fundamentally diverging perception of the political space than decades ago, it is of utter need to acknowledge this attitudinal shift among the whole electorate, but even more on the political left. Thirdly and finally, social democratic parties should not fear to reach out to social movements actors that had always been important in mobilizing and politicizing newly emerging cohorts of voters. Social democratic parties are well-advised not to repeat the mistakes from the past, where the long-term importance of those movements was if anything downplayed rather than emphasized.
In sum, while several political observers already wrote about a resurgence or revival of social democracy after recent electoral gains, it is at least questionable how sustainable this electoral trend is. While generational replacement is not a process that unfolds from one election to the next, it is of even bigger importance to analyze structural, long-term developments of the left electorates in Europe. For social democratic parties electoral fortune in the upcoming decades, it will be of crucial importance to attract new emerging generations of voters. If they fail to do so, social democracys electoral future does look rather grey than bright.
