They didn’t have room for all four graphs of the time-series decomposition so they just displayed the date-of-year graph:
They rotated so the graph fit better on the page. The rotation worked for me, but I was a bit bummed that that they put the title and heading of the graph (“The birthrate tends to drop on holidays . . .”) on the left in the Mar-Apr slot, leaving no room to label Leap Day and April Fool’s. I suggested to the graphics people that they put the label at the very top and just shrink the rest of the graph by 5 or 10% so as to not take up any more total space. Then there’d be plenty of space to label Leap Day and April Fool’s. But they didn’t do it, maybe they felt that it wouldn’t look good to have the label right at the top, I dunno.
Minor critique: I think there’s too much text in too strong a type. The graph gets a bit lost.
Do we know what fraction of births are scheduled in advance, either as induced labor or caesarian section?
C Sections alone are roughly 35% of births, I think.
Yes, about a third (http://www.cdc.gov/nchs/fastats/delivery.htm). But all c-sections are not scheduled, per question above.
This article (http://content.time.com/time/health/article/0,8599,2007754,00.html) suggests a rate of about 20% induction. Of those, roughly 40% may be elective. So maybe 8% of folks are setting out with a due date in mind. Probably not many choose Christmas.