PHOTO: Ivy Zelman

Ivy Zelman likes to do puzzles, big ones with 2,000 pieces. That helps explain how’s she’s able to assess thousands of disparate U.S. housing data points to assemble her closely followed market views. This ability—plus hard work and prescient calls on housing at both the top and bottom of the market—is why she’s among the best known and highest-ranked analysts in the industry. Her negative view on housing in 2006 also earned her the Wall Street sobriquet “Poison Ivy.”

What does she think about housing now? The CEO of Zelman & Associates, an ex-New Yorker with 27 years of experience, notes that home-building growth has slowed sharply of late and that inventory is rising in some regions and markets, like the West Coast and among luxury homes. Still, she sees this slowdown as a pause—but only if mortgage rates don’t go much higher. If they begin to approach 5 3/4%, affordability will become an issue, and all bets are off.