I don't.
I'm considered a baptized Catholic, because Catholicism teaches *once a Catholic, always a Catholic*, so anyone who was ever baptized Catholic is counted in their numbers, even if they've left the church and haven't stepped foot in it in decades.
And I know of several Evangelical and Protestant churches which are chock full of former Catholics, all probably still being counted on Catholic roles as part of that 1 billion strong.
Catholics themselves admit that the majority of those baptized are not practicing Catholics. They consider those who support abortion to have ex-communicated themselves.
Except for when they want to brag on numbers. Then they're part of the flock.
One billion strong my.... er ... foot.
Or when its time to be buried. Even if your name is Kennedy or Chavez!