My opinion is: they don't, only in hindsight.
Sure chances are there will be a reaction, but which one, 23, 32, 50, 61?
You've got a one in 4 chance..25% chance of getting the right level. What kind of odds are those to trade off
fibs are certainly controversial and fit in the voodoo category. my own thoughts are that a significant number of traders use them as evidenced by the chart. this information can be used to your advantage. just the same as if you see a stand out support and resistance level on a higher level time frame chart. The vast majority of traders will be looking at it and will know about it. Some will exit an onside trade there, some will initiate a position there, this information can be used to your advantage. GLGT