What are the best Y coordinates to find iron?

I have tried so many different coordinates and I can't seem to find the Y coordinates where iron spawns the most in Minecraft.

What are the best Y coordinates where iron ore is most likely to be found?

Iron usually generates below area level (63) rather evenly... The best way I found is to

1. Look thru ravines and caves (a stack of sand or gravel helps you easily climb cliffs, and a stack of dirt or cobblestone can make bridges fast)
2. Digging a shaft horizontally, then branching off every 3rd block with a run... Do this at level 12 and you will find iron, coal, redstone, diamond, and a cave or fortress or abandoned mineshaft!
3. (If you are playing"evil") you can find a city and kill their iron golem, but not really worth it for just a few pieces

From the Minecraft wiki, a graph showing ore distribution by height:

According to it, Iron should be most commonly found from Y=6 to Y=50.