Interest in investing in environmentally and socially responsible companies has surged in recent years, in part because of the tastes of purpose-minded millennials—but also because there’s mounting evidence that these companies are, in fact, better investments. That’s good news for the planet, but a more sustainability-minded financial system is hardly a given. A panel of experts at the Fortune Most Powerful Women International conference in Montreal, Canada on Tuesday discussed the challenges testing the burgeoning field.

Amy Oldenberg, COO of Emerging Market Equity for Morgan Stanley, said her team, which manages $20 billion in emerging markets investments has struggled with the quality of data when it comes to looking at companies in terms of their performance on ESG (Environment, Social and Governance) factors, metrics that are important for investors to understand what companies are run most sustainably and which investments are most impactful.

She pointed out that there is little data standardization in the fast-growing field and that more than half of companies, especially those in emerging markets, currently lack ESG coverage. She said that the murky quality of ESG data—Russia’s Gazprom rates higher than Exxon in one example she gave—that underlies sustainability indices make them hard to trust. “It’s very hard to put a score or figure out what the ESG component is that we can communicate to clients,” she said.

Nili Gilbert, co-founder of New York-based investment firm Matarin Capital, noted that the lack of standardization and the wide-ranging nature of ESG ratings and data sets overwhelm investors and companies, adding that the “cacophony of measurement” has become a main reason many dismiss it.

The panelists also discussed the field’s image problem. Oldenburg said Morgan Stanley has launched a robust education effort to familiarize traditional investors with sustainable investing and the sorts of ESG issues that they should focus on in each industry. She said that while some longtime investors are developing an interest, a number remain skeptical and consider ESG to be a marketing scam. “They don’t buy into it at all,” she said.

That skepticism is why BlackRock avoids the term ESG and instead uses the term “sustainable investing,” said Heather Loomis Tighe, a managing director at the $6 trillion-plus asset management firm.

“It’s fascinating,” said Tighe. “If you were to sit in front of an investment board and say, ‘There is an economic factor that is holding back from unlocking from 2 basis points to 2% of return on a consistent basis, would you like to explore it?’, the answer would be a resounding yes…When you sit in front of an investment board and say, ‘We’d like to take ESG into account,’ the response is no longer so resounding.”

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