• Active home listings dropped 7% in May to the lowest number Redfin has ever recorded going back to 2012.
• New listings, meanwhile, fell 25% year over year to 465,000 last month.
• That's due to high mortgage rates, which have discouraged owners from selling their homes.

The housing market is suffering its worst inventory shortage in over a decade, a sign that high mortgage rates are causing the housing ice age to drag on.

Active home listings saw a year-over-year drop of 7.1% last month, slumping to 1.4 million in May, according to data from Redfin. That's the lowest number of available homes the real estate analytics group has ever recorded, with its data going back to 2012.

New listings, meanwhile, fell 25% year over year to 465,000 last month – the third-lowest number Redfin has recorded.

The drop in available homes is largely due to high mortgage rates, with the average rate on the 30-year fixed mortgage hovering near a 20-year record at 6.35%. Rates that high discourage existing homeowners from listing their properties, as many financed their homes at ultra-low interest rates years ago.

The result is an unaffordable and largely frozen housing market, with the shortage in inventory pushing prices higher and slowing sales activity. 

In fact, 38% of properties last month sold above their listing price, Redfin said. Meanwhile, pending home sales dropped 16%, a sign that the spring homebuying rush has faltered in the face of higher mortgage rates.

"There are two things that would jumpstart the housing market: A big drop in mortgage rates and/or a big surge of new listings … Neither of those things happened this spring," Redfin's deputy chief economist Taylor Marr said in a statement on Thursday. "Instead, rates rose and new listings dropped to record lows. And with one or two more interest-rate hikes expected this year, mortgage rates are likely to remain elevated at least through the summer, continuing to limit both demand and supply."

Affordability and homebuying activity won't pick up until mortgage rates drop more meaningfully, Marr previously told Insider, though he said that was unlikely to happen anytime soon. He predicted mortgage rates would likely ease to just around 6% by the end of the year.