Are inventory increases caused by new listings or slower sales?

[Leo R.]

As we're all aware, inventory is increasing in many markets (though, in many instances this just means the market is going from very, very, very low inventory to very, very low inventory.).  ...It's sort of like "upgrading" from a golf cart to a Yugo...

Inventory can increase as a result of more people listing their houses, and/or by a slowdown in how quickly houses sell (an increase in days on market).

Are current inventory increases more a product of an increase in people rushing to list their houses -OR- Are current inventory increases more a product of a slowdown in how quickly houses are selling? (or, are each of these factors contributing equally to current inventory increases?).

My own subjective (quite possibly inaccurate) opinion is that both factors are contributing to inventory increases, but I really don't have any idea how much each factor is contributing--are new listings responsible for 10% of inventory increases? 80%?, 45%?...are increased days on market responsible for 20% of inventory increases? 85%? etc., etc.?.

Interested to learn from BP folks about this topic!