Make the Stock Widget display percentage change Is there a way to make the Stock Widget in iOS's Notification Center to display percentage change instead of price change? Any Cydia tweak?

In the Stocks.app you can switch between those and market cap by pressing the price change tile on the right.
Sorry, the answer is no, you cannot.

The only configuration available for the Stocks Notification Centre widget is Enabled/Disabled.

Other apps that provide Stocks reporting may have been updated to provide more configurable notifications, however the stock (sic) app does not.