The promise to build a massive border wall and send Mexico the bill is a key tenet of Donald Trump’s campaign. The Republican frontrunner has drawn criticism for neglecting to explain exactly how he plans to get our neighbors to the south to cover the costly project, so last week his campaign released a…creative proposal.

Trump plans to make it difficult or impossible for Mexican immigrants to send money home until their country’s government agrees to pay for the border wall, a project that is estimated to cost billions. The proposal has shined a media spotlight on international remittances.

In her remittances explainer, Vox reporter Dara Lind calls these transfers “a tremendous force in the global economy.”

“They’re essentially a shadow foreign aid system that’s bigger (and arguably more effective) than official foreign aid,” she says. “Immigrant workers in wealthier countries sent back roughly $435 billion to the developing world in 2015. According to the World Bank, that’s three times the size of official development aid from governments — and larger than private sector investment.”

But despite this boon to the developing world, remittances have become a lightning rod in the current political climate. Trump and many of his supporters are opposed to the idea of money flowing out of the U.S., particularly funds sent through untraceable channels. Many immigrants choose not to send money through traceable organizations like the World Bank, discouraged by costs, logistics, or the need for documentation.

Matt Oppenheimer saw first-hand how challenging international money transfers can be when he was working at Barclays Bank in Kenya. The experience inspired him to return to the U.S. to found Remitly. The Seattle-based startup provides a mobile platform for people in the U.S. to send money abroad with lower fees than traditional banks. In October, Remitly began offering transfers between the U.S. and Mexico, which is the world’s largest remittance channel.

We caught up with Oppenheimer to talk about money transfers between these two countries, a contentious issue this election season.

Q: What do you think of Donald Trump’s proposal to stop remittances to Mexico until the government pays for a border wall?

Oppenheimer: “Trump’s “proposal” is ridiculous. It’s pure rhetoric to get attention and to fire up the anti-immigration sentiment of his supporters. He uses fear, uncertainty and doubt to sell his vision. In addition to not being feasible to stop remittances, here’s what Trump’s rhetoric ignores: Immigration is not only a humanitarian effort, it’s a critical competitive strategy for U.S.-based companies to thrive in today’s global marketplace. Our country was built by immigrants, our cities and towns were developed by immigrants, and everything from low-skilled to high-tech services are staffed by immigrants. How do you reconcile anti-immigration policies with the fact that 40 percent of the Fortune 500 were founded by immigrants or children of immigrants — or that a quarter of all Americans who have won Nobel Prizes have been immigrants?”

Immigration is not only a humanitarian effort, it’s a critical competitive strategy for U.S.-based companies to thrive in today’s global marketplace.

Q: What are the consequences of making it more difficult to send remittances to Mexico?

Oppenheimer: “The flow of money between the U.S. and Mexico is the largest remittance channel in the world. People send more than $23 billion every year from the U.S. to Mexico. Many people are migrants who have moved to the U.S. to pursue a better life and they are sending back their hard-earned wages to help their families back home pay for things like rent, tuition, food, and bills. Cutting off remittances is not only discriminatory, counter-productive and impractical, it would have detrimental effects on our economy.”

Q: Do you think sending money to other countries helps the U.S. economy? What about the global economy?

Oppenheimer: “Absolutely on both fronts. For the U.S. economy, building a better life for loved ones back home is a primary reason people migrate to countries like the United States. As I mentioned, migrants do amazing things for the American economy like start 40 percent of our current Fortune 500 businesses and create more American jobs. For the global economy, migrants will send more than $588 billion from the developed to developing world this year – that’s many multiples more than the total foreign aid budget of all governments globally. We see the flow of money from the developed to developing world like any other utility – as vital as water and electricity.”

We see the flow of money from the developed to developing world like any other utility – as vital as water and electricity.

Q: Historically, remittances have been difficult to track. How can we make them more transparent?

Oppenheimer: “While some remittances are sent via informal networks, $588 billion is sent via formal networks that Remitly and legitimate organizations (like the World Bank) track very closely. The remittance industry historically lacked transparency around pricing. That’s something Remitly is working to solve. It’s core to our mission and vision to offer clear and transparent fees and exchange rates. Our customers deserve better so that’s what we’re giving to them.”

Q: Let’s switch gears and talk a little bit about Remitly. What’s next for the company?

Oppenheimer: “Remitly is growing rapidly. We grew the overall money transfers in our service by more than 400 percent year-over-year in 2015. We recently announced our customers are now transferring $1 billion annually using our service. In terms of what’s next, we’re focused on expanding our global footprint. We’ve strategically focused on bringing our service to the world’s largest remittance corridors first – we’ll be launching new corridors in coming weeks and look forward to sharing more on that soon!”

Q: What do you think the future of remittances will look like?

Oppenheimer: “Faster, more convenient, more connected experiences between sender and receiver. In the next five to 10 years, the vast majority of people will send and receive remittances via smartphones. This creates a huge opportunity to improve our customers’ lives and we’re really just getting started.”