Prominent bond investor Jeffrey Gundlach, the CEO of $140 billion DoubleLine Capital, nailed his bullish gold call from September 2018, and now he sees further upside for the yellow metal as the supply of negative-yielding bonds balloons.

"At this point, I think the way to think about it is, as long as the volume of negative interest rate bonds outstanding increases, it’s quite likely that gold moves higher in a similar vein," Gundlach told Yahoo Finance in an interview on Tuesday evening.

When looking at the markets broadly, Gundlach's view is that the global stock market hit its peak on January 26, 2018. And while certain indices did breach record levels again, not all of them did.

"The New York Stock Exchange Composite (^NYA) never did. The Transportation Average (^DJT) never did,” he said. “But then, one by one, the global stock markets started to slide during the middle of 2018. And finally, on October 3rd, basically, every index in the United States hit a peak or had previously hit a peak and then moved down very sharply into December 26th of last year, and I talked about that as being the start of a bear market.”

He also noted that economic data globally also peaked out in January 2018 amid that narrative of synchronized global expansion.

"We've never really seen economic data that strong since,” he said. “It’s held up better in the United States to October/November, but we have much worse economic data pretty much across the board."

Subsequently, central banks have responded with what Gundlach calls "increasingly negative interest rate manipulation."

As the amount of negative-yielding debt increase, gold prices will go up

"We are now, I think it's today or yesterday over $15 trillion of global debt is at a negative yield. And the US bond market is being dragged to lower yields by a combination of the race to ever more negative yields in parts of the developed world, and by weak economic data," Gundlach said.

With that backdrop, there's been a direct correlation between the volume of negative-yielding bonds in the world and the dollar price of gold that's moved up very much in sync, with very little divergence along the way.

As negative-yielding bonds moved from $10 trillion to $15 trillion in April and May, gold has moved up close to 20%. Gold futures (GC=F) settled at $1,473.40 on Tuesday. It was last seen around $1,517 on Wednesday.

"It makes all the sense in the world,” he said. “It's one thing when bonds yield negative a basis point. That's painful. This amount of pain isn’t really excruciating.”

“But now that you’re getting into some more significant negative yields, it’s not surprising that people might want to buy things that have a higher yield than bonds,” he added. “With the yield of 0, gold has a higher yield than bonds. And if you store the gold, you now have a lower cost of carry on gold than you have on 10-year bunds.”