Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of storage and data management company Iron Mountain Incorporated (NYSE:IRM) jumped 21% today after getting approval to convert to a real estate investment trust, or REIT.

So what: The IRS sent a private letter ruling to the company approving its REIT, status for fiscal 2014. As a result of the lower tax rate, management also raised earnings guidance from $1.37 to $1.52 per share and free cash flow without real estate by $50 million to $350 million-$390 million. 

Now what: REITs don't pay corporate taxes; instead they distribute at least 90% of taxable income to shareholders in the form of a dividend. Companies are moving to this structure to lower taxes paid overall and the number of industries using REITs are growing. This doesn't fundamentally change what's in the business, but it does change the tax structure. Investors are valuing that highly today, which is why the stock is up.