(NewsNation) — Decades of public opinion polling and academic research show the debate around abortion is more nuanced than a simple divide between those who are anti-abortion and those who support abortion rights.

Much of the data comes from the General Social Survey (GSS), a national biannual poll that asks Americans their views on a variety of social issues, including abortion. It allows political scientists, like Ryan Burge at Eastern Illinois University, to track the way public opinion has changed over time.

“Most Americans do not have a clear view of abortion, it really is situational and we’re very practical when it comes to abortion — we’re in favor in some circumstances, opposed in some circumstances, but it seems the general public is definitely not majority in favor of making abortion completely illegal,” said Burge.

Here are five ways Americans’ views have changed over time regarding the abortion debate:

1. Sharply contrasting views are a recent development

For almost 40 years, the American public’s views on abortion remained fairly static. In 1977, 36% of Americans surveyed by the GSS thought women should be able to get an abortion for any reason. Over the years, that number has fluctuated, peaking at 45% in 1994 before going back down to 44% by 2016.

But in the last five years, the percentage of people who say abortion should be available for any reason has increased rapidly to 54% in 2021.

Most of that increase is due to a considerable shift in attitude among Americans on the political left. Just six years ago, a slim majority of Democrats, 52%, said women should be able to get an abortion for any reason. Last year, that number rose to 69%, according to GSS data.

By comparison, Republican support for abortion has decreased since 1977 from 39% in favor of legal abortions for any reason to 35% in 2021.

2. most agree under specific circumstances

Although views on abortion have been mostly split along partisan lines, there are two instances where Republicans and Democrats overwhelmingly agreed that it should be legal — when a woman’s health is seriously endangered by the pregnancy or if a woman becomes pregnant as a result of rape.

In 2021, 95% of Democrats and 79% of Republicans said a pregnant person should be able to obtain a legal abortion if their own health is seriously endangered by the pregnancy, according to the GSS.

The same data showed that 92% of Democrats and 73% of Republicans believed abortion should be legal if the pregnancy was caused by rape.

The majority on both sides — 87% of Democrats and 65% of Republicans in 2021 — also agreed that abortion should be legal if there is a strong chance of serious health defects in the fetus.

But since the early 1980s, Republicans actually became less open to abortion in more extreme cases including rape and serious birth defects.

Four decades ago, 87% of Republicans supported abortion if the pregnancy was caused by rape — a number that has dropped 14 points since then. Meanwhile. 85% said major birth defects should be a case for legal abortion which is 20 points higher than those polled in 2021.

“We are seeing Republicans become less permissive of abortion in these more extreme cases and we’re seeing Democrats become more permissive of abortion in these elective cases, like they want no more children or they’re not married or they don’t have the money to afford more children,” said Burge.

3. men and women mostly agree

Abortion is often framed as a women’s issue but over the years, men’s and women’s views on abortion have largely mirrored each other. As recently as 2016, more men (44%) than women (43%) agreed that women should be able to get an abortion for any reason.

In 2021, women’s support for abortion surpassed men’s but only slightly — 56% of women supported it to 52% of men.

The small differences that exist between men’s and women’s views are mostly attributable to politics, not gender, Burge said.

And data suggests men and women agreed regardless of the reason for the abortion.

In 2021, the majority of men, 79%, said women should be able to get an abortion if there is a strong chance of serious birth defect, compared to 75% of women.

There was also agreement that women should be able to get an abortion if the reason for doing so is because the family can’t afford another child — 56% of women to 55% of men.

4. religious views vary

Views on abortion are widely skewed across religious groups and even among different races within those groups.

In 2021, only 26% of white evangelicals were in favor of “always allowing women the right to obtain an abortion as a matter of choice,” according to data from the Cooperative Election Study (CAE). Whereas, significantly more, 47%, of non-white evangelicals were in favor.

The same pattern is true for Catholics. In 2021, 50% of white Catholics were in favor of allowing women to choose compared to 66% of non-white Catholics, according to the CAE. Even more Black Protestants, 69%, support women’s choice.

“Religion does matter but it matters as an array of issues alongside other demographic issues, partisanship issues,” said Burge. “I don’t think religion is the most operative factor acting on people’s abortion opinions anymore.”

5. Pregnancy term matters

Perhaps the most important variable that influences Americans’ views on abortion is when in a pregnancy it occurs.

Surveys showed support for legal abortion remains high if the intervention occurs during the first three months of pregnancy but drops significantly in the second and third trimesters.

According to Gallup polling from May 2018, 60% of respondents said abortion should “generally be legal” in the first three months of pregnancy but only 28% thought so for abortions in the second trimester.

Only 13% of respondents, according to the same Gallup poll, agreed that abortion should be legal in the last three months of pregnancy.

But when the survey question is framed as a “ban” on abortion in the second trimester, respondents are far less supportive.

Only 41% of U.S. adults supported banning abortions after the eighteenth week of pregnancy, compared to 56% opposed, according to a May 2021 poll from Gallup.

It’s this nuance that makes gauging public sentiment on the topic extremely difficult.

“Just from a public opinion perspective, the vast majority of Americans do not want abortion to go away and the court is really stepping out here,” said Burge.