A year after Donald Trump's election to the White House, the Mexican peso rises and falls, in part, along with the tweets and threats of the 45th president.

The sincerity investors perceive in the president's threats to build a wall at the United States-Mexico border and withdraw from the North American Free Trade Agreement has affected the peso's movements since his surprise victory in 2016. The more worried Wall Street is he will act, the more the peso falls. And the more they think he's bluffing, the more it rises.

The peso spiked against the dollar on November 8, 2016, the day of the election, on expectations Democrat Hillary Clinton would win. It dove almost immediately after Trump was elected and fell even further as his inauguration approached. When then-Press Secretary Sean Spicer suggested Trump might impose a 20% tax on Mexican imports in January, the peso fell by about 1%.

But as Trump's rhetoric appeared increasingly disconnected from his policies, the peso rose again. After bottoming out at about 22 pesos to the dollar ahead of Trump's inauguration, by July, it was trading in the 17-18 range. It's trading at about 19 pesos to the dollar today.

The peso has begun to soften again as NAFTA talks have heated up among the U.S., Mexico and Canada. It's currently trading at over 19 pesos to the dollar, about where it was right after Trump was elected.

"Basically, if you see the daily series of the peso-dollar parity since mid-2016 to now, you can see the problem," said Alfredo Coutino, Latin America director at Moody's Analytics, in an email to TheStreet. "The main episodes for the peso have been November 2016, January to February 2017, and July to October 2017, which are mainly the times when Trump has threatened with withdrawing from NAFTA or asked Mexico to pay for the wall."

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To be sure, it's not all about Trump. Inflation in Mexico is high, and uncertainty about a potential interest rate hike in the country has investors on edge. Other recent events have had an effect as well.

"Mexico had two earthquakes in September, and growth was a little bit weaker in the third quarter than in the first part of the year," said Michael Klein, Tufts University economist and founder of economics website EconoFact in an interview.

Mexico's economy likely shrank for the first time in more than four years during the third quarter, according to a preliminary official estimate this week. 

The peso still hasn't returned to inauguration-level lows, despite the president's continued insistence on a border wall and increasingly testy negotiations on NAFTA. That may be, in part, because investors simply aren't taking Trump as seriously as they used to.

"The thing with Trump is that markets move on news, but the news has to be credible," Klein, former chief economist in the office of International Affairs at the U.S. Treasury Department, said. "Because Trump's views on things are so volatile, it's hard to see how his tweets and announcements can have much of an effect."

Commerce Secretary Wilbur Ross at an October 25 conference declared "the president is not a bluffer" on the subject of NAFTA. He told CNBC in a separate interview that the U.S. has no intention of making any concessions. "We're asking two countries to give up some privileges that they have enjoyed for 22 years," he said. "And we are not in a position to offer anything in return."

The same day, Mexican authorities intervened in the foreign exchange market and increased currency hedges in the local market. The mechanism, in place since February, is intended to reduce volatility.

The action caused the peso to rally, but Coutino in a note warned investors should still be wary. "Since the destiny of the trade accord remains uncertain, the peso is not free of further pressures," he said.

And of course, some of those pressures come from the man in the Oval Office. 

TheStreet's feature series "Inside Trump's First Year" looks at the biggest stories in business over the last year fueled by one of the most unpredictable presidents in history. Most importantly, TheStreet offers a glimpse into what could happen in 2018 on a range of issues -- and stocks -- in what will probably be an equally chaotic second year for Trump. Read more by tapping the photo below.

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