"We've had a steady stream of single women in all our programs, from international to African-Americans, adopting," said Sabra Larkin, director of communications for Spence-Chapin Services, an adoption agency in New York founded by a single woman, Clara Spence, in 1908.
"It goes alongside of the growing trend in adoption," said Barbara Turvett, an adoptive parent and the articles editor at Working Mother magazine. "It's becoming not just an acceptable thing to do, but a favorable thing to do. It's a great way to form a family."
Last month, Simpson, 25, who recently filed for divorce from her husband Nick Lachey, expressed her desire to adopt a baby from Mexico.
"I want to adopt," she told the entertainment TV show "Extra." "And I plan to adopt before I have my own kids."
Simpson cited Jolie, 30, as a role model for doing "amazing, amazing things and the international adoption rate just since her has skyrocketed."
Jolie adopted her first child, Maddox, from Cambodia in 2002, when she was still married to actor Billy Bob Thornton. The actress told the television program "Celebrity Justice" in 2005: "I prefer to adopt. With every adoption, I save a further child from the orphanage."
In March, Jolie went to Ethiopia with boyfriend Brad Pitt to adopt her second child, a then 5-month-old baby girl she named Zahara Marley.
But not everyone thinks single-parent adoption is a good idea. Arizona state Rep. Steve Tulley, the Republican majority leader, proposed legislation earlier this year that would have given married couples preference over singles in the adoption of children from that state's Child Protective Services agency. The bill failed by one vote on April 19.
"All this says is, all other things being equal, if a married couple is willing to adopt they ought to be given preference," Tully told the East Valley Tribune in Mesa, Ariz. "So far I haven't heard a good argument as to why that shouldn't be the case."
Dr. Janet Rosen, a clinical psychologist at Miami Children’s Hospital, was more mixed on the issue.
"Of course one stable married couple is the ideal," said Dr. Janet Rosen, a clinical psychologist at Miami Children’s Hospital. "It is very important to have both male and female role models and kids learn how to relate from their parents’ relationship. But it doesn’t matter if it’s male or female — one stable parent is more beneficial than two unstable ones."
Earlier this month, Families.com blogger Nicki Bradley posted a missive on Simpson's desire to become a mother. The suburban Detroit mother of six chided that the "celebrity motherhood 'fad' has gone off the deep end." Another poster responded that Simpson should adopt a puppy instead as "babies aren't accessories."
But Turvett said Jolie, for one, "obviously does it for all the right reasons."
"She's not infertile. She's pregnant right now [with Pitt's baby]. I think she just had this call. Something spoke to her," she said.
For Simpson, the desire to adopt may be traced to a Mexican orphanage, Casa Hogar Elim, which she visited as a teen. Others speculate the pop star/actress was ready to have children with Lachey and is not letting their divorce stop her.
Single celebrities who adopt can do so sooner than most American women because they are financially secure, Turvett said. "If you're going to be a single parent, you have to have some of your ducks in a row."
"If celebrities are younger when they are adopting, I think that's the reason, because I really do think you have to do some soul searching and because you've got to really figure out if you have the wherewithal financially, emotionally and physically to be a single parent," she said.
Other young starlets — such as Kate Hudson, Reese Witherspoon and Rachel Weisz — have shown that in modern Hollywood, it's acceptable to carry both a child and film a movie.
But with film salaries hovering in the millions, perhaps some actresses see adoption as a way of helping someone less fortunate than themselves.
Indeed, both Jolie and Simpson are active humanitarians: Jolie is a United Nations Goodwill Ambassador, and Simpson is an international youth ambassador for Operation Smile, which provides reconstructive surgery and related health care to indigent children and adults worldwide.
But do young celebrities adopting really influence the greater public?
"I don't think that I can attribute any adoption effect to Angelina Jolie yet," said Susan Caughman, the publisher and editor of Adoptive Families magazine. "Maybe it will become clear in years to come."
Caughman cites the increase in single-parent adoptions with the baby-boomer generation.
Last year, Americans adopted nearly 22,000 children internationally, according to Richard Fischer, the publisher of Adoption Today magazine, compared to the 121,000 kids adopted domestically in 2005.
Countries like China and Russia are open to single-parent adoptions, though some, like Korea, only allow two-parent families to adopt.
At Spence-Chapin, about 10 percent of the adoptions last year were completed by single mothers. About 25 percent of the membership of the national support group Single Mothers by Choice, which has has approximately 2,500 members, are adoptive parents.
Most of the single American women who adopt do so after age 35, like celebrity moms Sharon Stone, 47, who adopted a baby she named Laird Vonne Stone last May as a single parent (she adopted her first son, Roan, while married to her ex-husband); Calista Flockhart, 41, who adopted her son Liam on her own in 2001; Meg Ryan, 44, who adopted a baby girl from China this winter (the "Sleepless in Seattle" star also has a 13-year-old son with her ex-husband, actor Dennis Quaid) and "Sopranos" star Edie Falco, 42, who adopted a baby boy, Anderson, in March of last year.
"During the height of their careers, they're very busy moviemaking and promoting themselves and becoming successful," said James Robert Parish, a Hollywood historian. "And often times they either don't have time to think about or don't want to think about having a child."
The story mirrors that of the modern American woman.
"A number of professional women have gone from college straight into a profession and then put all their time and efforts into building a career and a lifestyle," said Richard Fischer, the publisher of Adoption Today magazine. "They realize they may not have the man or the person that they ultimately thought they'd have at this point, but there's no reason that they can't still have the family they always dreamed of."
While Hollywood's golden girls may not be on groundbreaking territory adopting children — by 1994, actress Mia Farrow had 14 kids, nine of them adopted — they do offer the added cachet of exposure to the cause.
"It brings recognition to the plight of many of the adoptive children," Fischer said. "I think it does more for the children than it does for the parents who would eventually adopt."