You're not going to think of a title without research. Since a huge chunk of EPQ marks are about planning, and progression, I have one bit of advice for you. Note down every step in the progression of your ideas somewhere. E.g. You wanted to do something to do with maths and economics, so you researched chaos theory in economics... You found ____, that lead you to think about ____. And so on.
That's how you'll find your title. As for what someone above said about it having to be more economics - absolute rubbish. The top exemplar I saw was completely mathematical, and I have two friends who did projects on mathematical economics and quantum computing, focusing on maths.
You can write about what you want. Just start reading journal/newspaper articles. Keep links to the web pages where you found them, and write down summaries of your thoughts. Continue like this over summer, and you'll easily have a bank of references for whatever you need to do. It'll also be helpful to keep notes on articles you decide you won't need to use - you can write about that in your project proposal and all the summary crap.
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