As a result, shares have climbed to $40.75 from $21 a year ago.
The company's shares climbed to $22 within the first three months.
The shares have climbed 14 percent in the last month.
The shares have climbed from a 52-week low of $30.10 in May.
In the last month, the company's shares have climbed more than 50 percent to close at $112 on Friday.
By 1991, that share had climbed to 60%, and it has been rising ever since.
Yesterday, the shares climbed to $14, but by late morning the price started to fall.
But the company's shares climbed well above the offering price.
The public share of health spending has been climbing gradually for decades.
This year, the shares have climbed to $56 at yesterday's close, from a low of $39.625 in March.