Like most things, the mana curve is not an exact science
For example, Naya Hexproof is becoming quite popular, so cards such as Celestial Flare might be good to consider in the sideboard, and Golgari and Junk Dredge is showing some play in tournaments as well, meaning Scavenging Ooze could also be another adaptation in the future
For example, I had a friend who loved making decks based around pop culture
However, the most common mistake people make is to confuse shadowless and shadow bordered Base Set Pokmon cards
If the card we were looking at was a PSA 9 card, it would tell you the number of PSA Grade 9 versions of that card that exist in the world under the population bit, and there would be a figure in the "Population Higher" bracket which would note the number of PSA 10 cards ie the only cards that scored higher than your PSA 9