CEO letters to shareholders usually elicit yawns but not when they're written by Jamie Dimon.

In his 28 page letter, the CEO of JPMorgan Chase pontificates on topics ranging from economic risks to partisan politics.

Dimon says his bank isn't predicting a recession, but it's prepared for one.

While admitting that investor reactions don't always accurately reflect the economy, he warns the volatility that rocked the global markets at the end of last year might be "a harbinger of things to come." He called for mortgage reform, adding that bad mortgage laws helped create the Great Recession of 2008.

In the aftermath of the crisis, the U.S. passed a series of bills to boost confidence in the mortgage industry and lower risks.

But Dimon says reducing what he calls "onerous and unnecessary origination and servicing requirements" would help boost economic growth.

The biggest threat to the U.S. financial system?

Cyber security, he says.

His bank spends $600 million on it each year.

But he says the bank must remain on guard because the financial system is interconnected.