This is a shiny app that uses Social Security Administration acturarial tables and cencus data to find the median age of a given first name.
The idea is from the Five Thirty Eight article How to Tell Someone's Name When All
You Know is Her Age.
Data comes from Hadley Wickham's babyname package.
The table lifetables give the mortality at every age in each cencus year. For
example, the first row shows that 14.6% of boys born in 1900 died before reaching
their first birthday.
We know from the babynames table that there were 9830 Johns born in 1900. Therefore
there were 8,395 1 year old Johns alive in 1901. We do this for each year and can
calculate the median age of Johns alive as of January 1st, 2014.
NOTE: Since the lifetables only give expectancies every decade, use linear interpolation to create expectancies for the years in between.