{
  "name": "Leap-day birthdays in the U.S.: inputs and results",
  "desc": "Every input and result of the estimate of how many U.S. residents have a February 29 birthday, one per row, with its source, data vintage and qualifier. The band is a range of inputs, not a confidence interval.",
  "lic": "CC BY 4.0",
  "lic_url": "https://creativecommons.org/licenses/by/4.0/",
  "by": "The Yardstick Almanac",
  "url": "https://theyardstickalmanac.com/scale/leap-day-birthdays/",
  "from": [
    "U.S. Census Bureau, NC-EST2025-AGESEX-RES (Vintage 2025, resident population by single year of age, July 1, 2025), released April 2026",
    "FiveThirtyEight data repository, births/: US_births_1994-2003_CDC_NCHS.csv (CDC National Center for Health Statistics) and US_births_2000-2014_SSA.csv (Social Security Administration), CC BY 4.0",
    "Gregorian leap-year rule, Explanatory Supplement to the Astronomical Almanac, ch. 15, sec. 15.4.2"
  ],
  "how": "Compiled by The Yardstick Almanac from the data listed",
  "data_by": [
    "U.S. daily births 1994–2003 (CDC NCHS) and 2000–2014 (SSA) from the FiveThirtyEight data repository, CC BY 4.0 (adapted: birth ratios computed); Census Bureau Vintage 2025 population by age, July 1, 2025 (public domain); computed 2026-11-01, CC BY 4.0"
  ]
}