I'm just wondering, after reading this quote on Michael Munger's blog.

On the subway, Peter asked, 'Shouldn't we consider having triplets?' And I had this adverse reaction: 'This is why they say it's the woman's choice, because you think I could just carry triplets. That's easy for you to say, but I'd have to give up my life.' Not only would I have to be on bed rest at 20 weeks, I wouldn't be able to fly after 15. I was already at eight weeks. When I found out about the triplets, I felt like: It's not the back of a pickup at 16, but now I'm going to have to move to Staten Island. I'll never leave my house because I'll have to care for these children. I'll have to start shopping only at Costco and buying big jars of mayonnaise. Even in my moments of thinking about having three, I don't think that deep down I was ever considering it. -- Amy Richards, an abortion rights advocate, describes her decision to kill two of her babies, leaving her with a single baby, instead of having triplets

Here's one answer to the elasticity question.