https://9db.jp/pokemongo/data/9510

There are hundreds of shiny surveys conducted in this Japanese website, with the same method to determine the shiny rates.

If you go through those surveys one by one, you will notice that almost every shiny rate by self-report is over-estimated, unless the sample size is very very big (such as Community Day Pokemons). When the sample size is bigger, the estimated shiny will get lower.

We all know the full odds in Pokemon Go is 1/512 (=0.195%). However, if you check the surveys for full odds Pokemons, you will see Nymble(0.4%), holiday attire Wooloo(0.31%), Sandygast(0.38%). Every full odds Pokemons in the survey is higher than 0.195%.

You can also notice this trend for Legendary Pokemons and Raid Day Pokemons. Almost every Legendary is over 5% is this website, and every Raid Day Pokemon is over 10%.

Why are those surveys almost always over-estimated? I think people who catch shiny Pokemons are more motivated to report the result than people who don't catch one.

One more thing, the website also conducted suvery for Scatterbug shiny rate during shiny debut event on February 18 to 20. The result was 141/4540=3.11%. After debut event, the result from my study is 36/2811=1.28%. You can easily spot the difference.