Let's do the MATH...I think, you didn't read correctly...I said in 1 year. Therefore, One year ago, the share was $36. It is now $18. So, if I say, 50% of today's price $18, it would be $27 a year ago. Since, the price is $18 today, the year go it was $36 therefore it is 100% from today's price.
No, you're arithmetic is incorrect. Today's $18.00 (now $17.90) represents a 50% devaluation from a $36 share price. However, to get back to $36 share value it must now increase by $18 or 100%. A much tougher task. qed