What are the chances of getting a lucky Pokémon?

There are two ways to guarantee a lucky Pokémon:

• You are guaranteed a lucky if you, or the trainer you are trading with, has acquired less 10 lucky Pokémon AND either Pokémon's capture date is July 2016 or August 2016 (Source)

• With the new feature of lucky friends, trading while lucky friends will guarantee a lucky Pokémon. Lucky friendship status has a random chance to occur once per day when sending gifts, raiding, battling, etc with a best friend. (Source)

Outside the two situations where a lucky Pokémon is guaranteed, SilphRoad had done a lot of research on the chances. As shown on their site, below are the average rates for lucky Pokémon based on the capture date of the Pokémon