How does a family become a family? Well, when two people love each other very much ... I’m joking, I’m joking. Kind of.

As we discussed last week, American families often form around marriages. So, romantic relationships can be a first step in the stages of family life. It might seem strange to think of dating as a part of family formation. After all, when you're swiping right on Tinder, you’re probably not thinking about adding that person to your family.

But, families are a dynamic social institution, changing over the course of your life. What the word 'family' conjures in your mind is going to be very different when you’re 16 versus when you’re 60. Sociologists say that every family has a lifecycle; they form, they change, and they sometimes break apart. 

When we we talk about the stages of family life, we’re usually talking about organisms; the lifecycle of a mayfly, or something like that. But, just as you pass through developmental stages from childhood to adulthood to old age, a family evolves as well. 

Sociologists describe this process as the family lifecycle, the developmental stages that a family passes through over time. Of course, individual families are different. Some people might move through the stages of family in a different order or skip some stages altogether. But, these stages are meant to describe the typical lifecycle of a modern American family.

The first stage of family is very cute, it's courtship. I'm sure you know what courtship means, but in case it's on your final, it's the period of developing a relationship with an eye toward marriage or long term partnership.

So, how do people pair off in different societies? Well, some cultures, including the US, put a heavy emphasis on romantic love as the foundation of a partnership. Finding 'the one' is wrapped up in an idea that a relationship should be based on affection, attraction and passion for your partner.

Other cultures practice arranged marriage, in which a marriage is negotiated between two families in order to create stronger bonds between them. Love isn't considered a prerequisite for marriage, though parents may consult the children's feelings when picking a spouse. If the married couple's shared life eventually creates bonds of affection, that's a bonus.

For those in cultures that celebrate romantic love, the idea of an arranged marriage often seems completely unthinkable. It's important to recognize though that, even in the US, sex and romance typically aren't the only foundation of a long lasting relationship.

Passion is often a less stable basis for a relationship than marital arrangements based on social and cultural compatibility. When the passion fades, if there aren't other foundations for the relationship, it may fall apart. And, in fact, even in countries that emphasize romantic love, societal forces often 'arrange marriages', based on who is socially, economically and morally compatible.

Societies often encourage homogamy, or a marriage between people with similar social backgrounds, like educational achievement or class standing. 

Another common factor in romantic love is propinquity, or a physical proximity to another person. Doesn't sound very romantic, but we tend to end up with people who are just 'around', because we often live near people like ourselves.

Now, of course courtship doesn't always lead to marriage. In fact, in recent years, marriage rates have been declining in many high income countries - partially due to people waiting longer to marry, and partially due to people forgoing marriage altogether.

Among women between 35 and 44 in 2010, around 20% had never been married. In comparison, for the previous generation at that age, only 10% of women had never been married. Even with declining marriage rates, most Americans will marry at least once.

Marriage, and particularly weddings, are often seen as a life goal; something to aspire to. Weddings are not marriages, of course. And for many this stage of settling into a new family comes with changes in expectations of what married life will look like. 

How a couple handles the transition from courtship into marriage is an important predictor of family stability. Some find that once the honeymoon stage ends, that is the first couple of years of marriage when everything is new and exciting, they are no longer satisfied in their marriage.

To find passion, some turn to infidelity, which occurs more often than you might think. In an anonymous survey of approximately 900 Americans, researchers from the Kinsey Institute for Research in Sex, Gender and Reproduction at Indiana University found that 19% of women and 23% of men report cheating on their partners at least once.

One outcome of infidelity that may not surprise you is divorce. You might have heard that half of all marriages end in divorce, but that's not quite accurate. For one thing, it's not that every couple as a fifty-fifty chance of divorce. 

The 50% stat comes from looking at the likelihood that marriages reach a certain anniversary. How likely are you to still be together 5 years after marriage? What about 20 years? For couples that marriage 40 years ago, we know what percent of those marriages have ended in divorce. And, that's a decent proxy for how many will ever end in divorce. 

For Americans who married in the 1970s and 1980s, about 40 to 45 percent of those marriages have ended in divorce. There was huge surge of divorce in the 1970s, in part due to many states loosening their restrictions on who can divorce through no-fault divorce laws, which allow couples to divorce for any reason.

Prior to no-fault laws, divorce was only allowed if one spouse could prove abuse, abandonment or adultery. Along with the removal of legal barriers, social norms also changed, with divorce becoming more socially acceptable. Plus, increased opportunities for women in the workforce make it more feasible for women to leave bad marriages because they were better able to support themselves and their children without a husband.

But, the divorce rate in the US has been on the decline since the 1990s. Some estimates suggest that the percent of marriages ending in divorce for more recent generations will be closer to one-third than one-half.

Why has it declined? Well, for one thing, fewer people are marrying, and fewer people are marrying young, with more people waiting to find a partner until they're more settled, marriages have become much more stable than they were in previous decades. Plus, the type of people who get married, and their likelihood of divorce, has changed, too.

Divorce rates are higher for low income and less educated Americans - who are also the socioeconomic group with the greatest declines in marriage rates in the last 40 years. So, the fewer who get married, the fewer who get divorced.

Changing marriage patterns has also meant changing patterns in the family lifecycle, like when people have kids. While child bearing is typically thought of as the stage in the family lifecycle that follows marriage, the percent of children born outside of marriage has been increasing, with about 40% of all births to unmarried mothers.

There are also increasing social class divides in who has kids before or after marriage. While only 9% of births to college educated moms take place outside marriage, 58% of births outside marriage are to women with only a high school diploma.

But, regardless of whether having kids comes before or after marriage, this stage in the family lifecycle is an important one.

Let's go to the Thought Bubble to talk about our next family life stage - child rearing.

What a family looks like has changed a lot in the last couple of centuries. In pre-industrial America, large families were much more common, partially because of a lack of effective birth control, partially because having more children meant more hands to help with the work on a farm, and partially because higher rates of child mortality meant that many kids didn't live to adulthood.

But, as child mortality rates declined, and the US industrialized, the average family size declined from 7 children in 1800 to 3.5 children by 1900. Nowadays, birth rates are even lower. The old adage about  the American dream being a house with picket fence, a dog and 2.5 children isn't too far off.

The average American mom has 2.4 children, and this rate has been pretty stable for the last 30 years. But, when women have children has been changing.

In addition to delaying marriage, women are also postponing having kids. The average age at first birth is 26, up from 21 in 1970. Some of this is due to increased access to birth control, which allows people to better control the timing of when they have a child. And, some of it is because raising a kid is expensive. Many people want to wait until they're older and in a more financially secure position before they add a third mouth to feed.

The US Department of Agriculture estimates that for kids born in 2015, the typical middle class family will spend $233,000 on that kid over the course of their childhood. Clothes, food, toys, transportation, basic education, medical care - it all adds up pretty fast. And, that figure isn't even accounting for the cost of college. But, even if the cost is high, being a parent is highly valued in American society.

A 2010 survey found that the majority of millennials say that being a good parent is one of the most important things in life, ranking it higher than having a successful marriage.

Thanks Thought Bubble.

The next stage of family life is the launch stage, in which kids grow up and leave their parents' house, usually in their early twenties. Though mom and dad might suffer from some empty nest syndrome when the kids first leave, many remain involved in their kids' lives, often providing childcare for their grandchildren once their kids start having families of their own.

This post-children stage of family life is the final part of the family lifecycle. Additionally, as lifespans increase, many adult children find themselves in care giver roles for their aging parents.

The sandwich generation refers to people who care for their aging parents at the same time that they provide care for children living in their household. This is particularly common for women, who are more likely to take on care giving roles in a family.

As I said at the beginning, these stages of the family lifecycle are just one path that a family can follow. There are all types of families and not all of them will be nuclear families with a mom, a dad and a bunch of biological offspring.

For one thing, a married couple doesn't need to be a man and a woman.  In 2015, the US Supreme Court made marriage equality the law of the land and ruled that all states must recognize marriages between same-sex couples. 

For another, not all married couples have, or want, children. Plus, not all families with kids have two parents. Single parent families make up about one-third of all families with children. Single parent families are most often headed by a single mother, rather than a single father.

There are also large racial differences in family structure, with 66% of black children being raised in a single parent home, compared to only 25% of non-hispanic white children. 

Some of these kids are still growing up in households with two parents, though. Fifty-eight percent of unmarried births were to cohabiting couples, or couples who live together without being married. Unmarried or divorced parents may also marry someone new, creating a blended family with one parent in a household who is unrelated to some or all of the children.

So, there's a lot of diversity in what a family can look like, but they often tend to follow similar paths. But, no matter what a family looks like, the family lifecycle helps us understand how families evolve over time.

Today, we looked at one way of thinking about the different stages of family life - courtship, marriage, child rearing and family life in your later years. We also discussed changing patterns of marriage and child bearing in the US, highlighting some of the varied family types that exist.

Crash Course Sociology is filmed in the Dr. Cheryl C Kinney Studio in Missoula, Montana and it's made with the help of all of these nice people. Our animation team is Thought Cafe and Crash Course is made with Adobe Creative Cloud.

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