In light of Amazon announcing that 50% of their units are being filled through consigned inventory, thought it would be worthwhile to highlight a few points from Baird's recently updated Q4 Amazon numbers:

Prime membership is now up to 48.5% of US households. This is up significantly from 39.5% in Q4 of 2015. The numbers above would assume 55-60 million of the total 125 million US households now have Prime.
45 million items are now Prime eligible vs 38 million in Q4 2015. This is a slight deceleration in growth from 28% year over year to 24% year over year.
Fulfill by Amazon (FBA) consigned product growth is up 24% year over year vs 37% last quarter. This also compares to Amazon's own product growth of 17%.

What does this all mean? Amazon is getting tougher on what can be added to their various sites as they fight unauthorized brands while the Prime membership grows and the amount of items in the Prime network increases. A healthy grooming needed as they continue to grow their audience.