It’s always the same old question.

The cashier at our grocery store asks me. The parents at the playground pester me. The lunch lady at my daughter’s school straight-out scolds me.

“No more kids for you?” she says, handing out chocolate milk to 40 clattering kindergarteners.

“One is enough,” I say. It’s what I say every time she asks.

“It’s very bad to have only one,” she says. “Angie needs a brother or a sister. She’ll be lonely.”

How could anyone possibly be lonely in a cafeteria that sounds like Times Square on New Year’s Eve?

Strangers always want to know when I’m having more children. When my answer surprises them, they point out all the ways I am ruining my daughter’s life by raising her as an only child.

She will be shy, lonely, bossy and spoiled, they say. She won’t learn how to make friends or take care of herself.

“Oh, you’ll change your mind,” the lunch lady tells me. “You’ll see.”

No, I really won’t. And neither will many others like me, according to new data on family size.

U.S. Census Bureau figures show that the number of women with one child has doubled from 10 percent to 20 percent over the last 20 years. Families with single children are the fastest-growing family demographic in the country.

Still, there is the social expectation to have more kids. In a study by the Pew Research Center, 46 percent of Americans said it is ideal to have two children. Only 3 percent said it would be ideal to have one child.

The reasons for the shift toward smaller families are varied and personal. Men and women are marrying later and delaying the start of their families. More mothers are working, out of economic necessity or professional desire. More women are raising children as single mothers, whether by choice or by result of divorce.

As for me, I have always wanted just one child. I adore everything about Angie — even the things that drive me crazy — and I cannot imagine loving anyone as much as I love her.

The lunch lady may disagree, but she doesn’t know that I am a single mom. She doesn’t realize that I have my hands full with this child — this headstrong little girl who refuses to put on shoes and socks in the morning and asks me to make her chicken noodle soup only to turn her nose up at it 10 minutes later.

There is another reason why I have decided to have only one child.

After Angie’s father and I separated, I found myself confused and alone with a needy, demanding 2-year-old. Being a single mom threw me for a loop, and it took about a year to get the hang of it. Now I have more confidence in myself as a parent, but I doubt I could ever again trust a man enough to have a baby with him. How do you rely on somebody like that, knowing he could leave one day too?

I love being Angie’s mother, but a mother is not all I want to be. I want to write books, climb mountains and learn how to paint. I want to be alone in the bathroom for more than six seconds. And now that my daughter is getting older, I can start thinking more seriously about some of those goals.

I still get teary-eyed in the baby aisle at Target. Those itty-bitty socks and fuzzy pink sleepers get me every time, but the longing I feel isn’t for a new baby. It is for the impossibility of reliving those first few years with Angie. I want to smell her newborn skin again. I want to hold her soft, bald head in my hand and kiss her little nose. If I could, I would hit the reset button, over and over, so she would never grow up and never leave me.

But I can’t. So I buy the cute socks and the adorable sleepers and ship them to my girlfriends who are having their second and third babies. Then I come home to the one and only person who will always be my baby, now matter how old or bossy she gets.

Wendy Fontaine’s “Party of Two” column appears every other week. Her email address is [email protected], or follow Party of Two on Facebook.