On Sunday, roughly 61.5 million voters will decide on the future government of the European Union's most populous country and biggest economy. Who will get to sit in the Bundestag, Germany's federal parliament? Who will be part of Germany's next government? Amid the refugee crisis in Europe and Donald Trump's isolationist policies, Germany has become even more of a key player in global politics. All eyes are on it — but who are the voters who will be deciding the country's fate?

Read more: Opinion: Germany votes and the whole world is watching

Who are the voters?

German voters are predominantly older and were born in Germany to German parents.

People who are 70 and older are the largest voter group by age — they make up 20.7 percent of the electorate, while voters under 31 account for just over 15 percent, according the Federal Office of Statistics (Destatis). Women make up 51.5 percent of the German electorate.

An estimated 10.4 percent of voters have a "migrant background." In Germany, this term is used to refer to immigrants and the descendants of immigrants — or, more precisely, to Germans who were not born German citizens or have at least one parent who was not born a German citizen.

Over half of these voters have roots in Poland (14 percent), Turkey (12.5 percent), Russia (12.5 percent), Kazakhstan (10.6 percent) and Romania (4.8 percent).

Who is (not) allowed to cast a ballot?

In Germany, any citizen over the age of 18 is allowed to take part in the federal election, with some exceptions:

• People who have a legal guardian are not allowed to participate in the election. In the last election, roughly 81,000 German adults were barred from voting because of this, according to a study commissioned by the Labor Ministry. This primarily includes people who have a developmental disability such as Down Syndrome.
• Also banned from voting are people in psychiatric care who have been declared not criminally responsible for a crime they committed because they suffer from a mental illness. This affected 3,300 Germans in the 2013 election. People with mental illnesses are, however, not generally excluded from the ballots.
• While almost all convicted felons retain the right to vote in Germany, a judge can ban someone who is guilty of a politically motivated crime from voting for up to five years. These cases are, however, extremely rare. 

Germans living abroad are generally allowed to cast a ballot, though they have to fulfill some requirements to prove their ties to their home country if they're staying in another country long-term. While Germans based in the country are automatically registered to vote, Germans living abroad have to register to vote for every election.

The 10 million foreigners living in Germany cannot partake in federal or state elections.

Read more: German election ballot box closed to 7.8 million residents

Who turns up to vote — and for whom?

Older Germans usually show up at the polls at significantly higher rates. In the last federal election, voter turnout was highest among people aged 60 to 70, while turnout was lowest among 21- to 30-year-olds. This trend has benefited Angela Merkel's moderate-conservative CDU and its CSU sister party in the past three parliamentary elections, given that the CDU and CSU tend to perform better among older people. (In the last election, they received over half of all votes cast by people 70 and older — compared to 41.5 percent of all votes from the overall electorate.)

Read more: German election: Will non-voters decide the outcome?

Electoral participation tends to be significantly higher in western German states. In the 2013 Bundestag election, voter turnout was 5.3 percent lower in eastern states, according to the Federal Election Commissioner. Eastern German states, which were under communist rule until 1990, are seen as strongholds of both the socialist Left party and the right-wing populist, anti-immigrant AfD, as well as hotbeds for other far-right extremists.

Women and men have voted at almost the same rate in the past few elections. In 2013, 72.1 percent of all eligible female voters cast their ballots, just 0.6 percent less than male voters. While Merkel's CDU and the Greens were favored by women in the last few elections, the Left party, the pro-business FDP, and in particular the AfD tend to attract more male voters. 

While the voting behavior of migrants and the children of migrants are not tracked as closely as voter preferences based on gender and age in Germany, a 2016 study commissioned by the Federal Migration Commission found that significantly fewer people with a migrant background were planning to cast a ballot than those without a migrant background, though second-generation immigrants were more interested in the elections than their parents.

Voter turnout projections varied for people from different ethnic backgrounds. People with roots in Eastern European countries expressed more interest in the Bundestag election than those of Turkish origin. 

The study found that 69.8 percent of people with Turkish roots tend to favor the social democratic SPD. This figure is more than twice as high as the projections for the party in national polls. Eastern European migrants and their descendants favored Merkel's CDU/CSU party and the AfD. The far-right populists have made headlines with their attempts to sway Russian and Polish-German voters away from the CDU/CSU.

Read more: Ethnic Germans from Russia in open letter: 'We are not the AfD'