[Yvain]

5,523 before December 25, when I posted the pre-registrations. 2,254 after.

Of the before-posting people, 2199 had exactly one sibling, and 71.1% of those were the older.

Of the after-posting people, 776 had exactly one sibling, and 72.3% of those were older.

A t-test revealed no difference between the two groups, p = 0.527.