Donald Trump's election as U.S. president has investors in JPMorgan Chase (JPM) - Get Report and Goldman Sachs (GS) - Get Report salivating at the prospect of fatter profits as costly financial regulations are rolled back.

But the more certain windfall might come from just trading on the president-elect's tweets.

Trump's surprise victory in November led to a surge in trading at the firms, as Treasury-bond yields climbed and stocks rallied in anticipation of economic stimulus and faster inflation under the incoming administration. On Friday, JPMorgan reported its best-ever trading performance for a fourth quarter, with total revenue from its markets business increasing by 32% to $5.68 billion.

Now, with the Jan. 20 inauguration fast approaching, some analysts expect another frenzy of trading this quarter, as the often-unpredictable Trump unveils the agenda for his first 100 days in office -- including measures on the economy, corporate taxes and import tariffs that could send bond, stock and currency markets on wild gyrations.

Anything from Trump that triggers positive market sentiment would lead to heightened trading, as investors move more cash off the sidelines, said Ken Leon, a three-decade Wall Street veteran who now serves as a stock analyst at research firm CFRA in New York.

"Or you could just see increasing volatility because he's changing the way investors think about different securities," Leon said.

It wasn't just JPMorgan that profited in the fourth quarter from the flurry of post-election transactions. Bank of America (BAC) - Get Report said trading revenue climbed 15% to $2.81 billion, and Morgan Stanley (MS) - Get Report reported a 49% jump to $3.19 billion. Goldman Sachs, which reports Wednesday, probably got a 19% revenue gain in the business, and the increase was probably 21% for Citigroup (C) - Get Report , based on Deutsche Bank estimates.

And that's before Trump even takes office.

Already the president-elect has roiled markets with seemingly unrestrained, unfiltered posts on Twitter. Such blasts have marked a dramatic departure from prior administrations' policy announcements and speeches that were vetted and negotiated carefully prior to public disclosure.

In December, Trump tweeted that the United States must "expand its nuclear capability," sending shares of small uranium miners soaring. Lockheed Martin's stock slid after Trump tweeted that the company's F-35 fighter-jet program was "out of control." Boeing's stock price dropped after Trump tweeted, "Cancel Order!" in reference to the company's contract to build a new Air Force One, the presidential airplane.

As a result, one startup has developed a "Trump Trigger" option that will notify investors when the president-elect mentions stocks they're following.

In the foreign exchange markets, any Trump policy announcements on China, Mexico or Russia could roil those nations' currencies.

Early indications are that trading firms are already seeing strong trading activity in 2017.

During a conference call Friday, JPMorgan CFO Marianne Lake described the first quarter's trading activity as, "so far, so good."

"There will be a lot of micro and event-driven activity" this year, she said. "And as long as it's not discontinuous, we should be able to intermediate transactions with our clients. And so far, generally there's been more risk appetite in the investor base."

At Bank of America, the trading business is diverse enough that declines in one area are usually eased by a pickup in activity in another, CEO Brian Moynihan told analysts on an earnings call.

"The good news is the United States strengthens in the first part of the year," he said. "We've seen a good normal first quarter developing and we've seen customer activity strong, all of which bodes well."

Get your trading triggers ready.

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