CHART OF THE DAY: Yahoo Shares Are Quietly Soaring Under Marissa Mayer

When you weren't looking, Yahoo's stock soared 50 percent in the last year. In this chart, we mark off the major events since Marissa Mayer was named CEO.

The three big reasons for the stock's lift: Mayer brings some excitement to the company, she's returning billions in cash to shareholders, and Yahoo still has valuable stakes in Asian tech companies.

This is a nice lift, but it's also something of a sugar high. Yahoo's fundamental earnings performance hasn't improved dramatically. All the goodwill Mayer has built with investors could evaporate if she doesn't improve its business.