Since 1880, the Census Bureau has asked people to describe their household relationships. In 1990, "unmarried partner" was added as a possible answer to the census question.
That one change shows how times have changed.
In 2000, 5.5 million unmarried couples were living together, up 72 percent from the 3.2 million couples who reported they were living together in 1990, according to a Census Bureau report released this year.
When you move in without the legal protections of marriage, you need to do more planning than deciding what curtains to hang. The fact is that many couples living together need to consider the financial and legal consequences of their arrangement, according to Violet Woodhouse, a financial planner, divorce attorney and author of "Divorce & Money: How to Make the Best Financial Decisions During Divorce."
"Divorce laws set lots of rules when a marriage ends," said Woodhouse. "But there's no law governing a split between unmarried partners. Without a cohabitation agreement, you and your ex-partner could face a financial and legal mess."
Woodhouse says that if you are already living together or planning to share a residence, there are some points you need to consider:
Estate planning is a must. Get a will. Without one, assets may not automatically go to a surviving partner but rather to family members or the state, depending on where you live.
Get a durable power of attorney for financial matters and a health care proxy for medical issues. "Unless you don't think the relationship is ever going to end or neither of you are going to die, you need to fill out these important documents," Woodhouse said.
Put all oral agreements in writing. This legal document is sometimes called a "cohabitation agreement."
For added legal protection when creating a cohabitation agreement, make sure you are each represented by an attorney. An attorney is more likely than the partners to spot all of the issues that need to be included in the agreement. Also, both parties being represented would likely eliminate claims of unfairness or duress if the relationship falls apart, Woodhouse said.
Do your research. Property and tax laws continue to be proposed and changed for the benefit of unmarried partners, especially for same-sex partnerships. Many employers now offer domestic partner benefits such as health, life and disability insurance, family leave, tuition assistance, relocation and travel expenses.
For more information get "Living Together: A Legal Guide for Unmarried Couples" by Nolo, a leading provider of self-help software and legal books. This book provides lots of practical advice and also includes information about various state laws relating to unmarried couples.
According to Nolo.com, here are several clauses couples should include in a cohabitation agreement:
Property Clause. The agreement should cover all of your property -- including the property you had before you began the relationship, as well as the property either or both of you accumulate during it. You should especially spell out who gets to keep what in the event of a breakup.
An expense section. For example, the document would detail how you will divide the day-to-day costs for food, utilities, laundry, housing and the like, especially if expenses increase or decrease.
A separation or death clause. It's wise to include at least brief provisions in your agreement stating what will happen if you split up, or if one of you dies. You may simply want to say that if you separate, each of you will have the right to take immediate possession of your separate property and that all jointly owned property will be divided equally. If there is property that you own together but not in equal shares, you'll want to specify a method for dividing it between you.
A dispute resolution clause. Couples should include in their agreement a method to resolve disagreements. For instance, they may choose mediation, where an impartial mediator helps the parties to negotiate.
"People's expectations change over time so it's important to have clarity if you decide to live together," Woodhouse said.
While Michelle Singletary welcomes comments and column ideas, she cannot offer specific personal financial advice. Her e-mail address is firstname.lastname@example.org. Readers can write to her c/o The Washington Post, 1150 15th St., N.W., Washington, D.C. 20071.