The wish to follow reliable sources is a good motive. The 41.3% number was not in any of those sources. Here are what the sources say: USA Today Money – 65%, Yahoo Finance – "some 50%", Independent Journal Review – "57.32% drop", Wall Street Journal – "down around 50%", CBS San Francisco – "more than 50 percent", San Jose Mercury News – 52 percent, Market Watch – "more than half", Forbes – "During Fiorina’s tenure HP’s stock price collapsed from $36.58 to $18.68". So we can try and summarize these numbers with a vague approximation or we can tell the reader all the numbers that appear to be reliably published.