NEW YORK (TheStreet) -- New laws haven't made banks safer than they were before the 2008 financial crisis, former Treasury Secretary Larry Summers said in a paper he co-authored for the Brookings Institution.

The article is set to be presented at a conference on Thursday, which marks eight years since the Lehman Brothers' bankruptcy filing, CNBC reports.

While "the Dodd-Frank measures to raise capital were very constructive," market data shows that banks are still in danger, Summers said in a guest appearance on CNBC's "Closing Bell" Thursday afternoon.

The "puzzle that our paper points out" is that if banks were "much better capitalized" then "their equity would become much less volatile," "their beta to overall stock market would go down," "the yield on their debt as it got safer would go down," and "their preferred stock which was backed by larger quantity of common equity would have a lower yield," he claimed.

But that's not what the market data shows, Summers added.

"If you believe in looking to market evidence, you don't see the kind of dramatic improvements that I think you would have expected," he explained.

Now there is "a nontrivial probability of at least a major loss in equity value by a major institution sometime in the next few years," the two researchers wrote in the paper. That predication is mainly a result of banks losing franchise value due to "regulatory activity and the prospect of future regulation," they claimed.

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