Published online by Cambridge University Press: 07 August 2017
A review is presented of PN birth rates. The observational determinations for other galaxies are compared with theoretical predictions based on stellar evolution models. The galactic birth rate is derived for different distance scales and is compared with the predicted one from galactic models of the solar neighborhood and with those determined for other galaxies; to reach agreement between observations and predictions long distance scales to PN have to be adopted. The total number of PN is estimated for the Galaxy and other galaxies.