This shows the female-percentage of people named androgynous names over time.
This normalizes each of the paths by start date by resetting the domain of the x-axis to fit each data row. Start date is defined as being the first time when the name had a female percentage greater than zero.
It would be much better to show the date on hover rather than simply the name. This would require a bit more precomputation because of the non-linear interpolation (can’t simply use scales).