The inventory crunch shows little sign of letting up. In the fourth quarter of 2013, inventory dropped to 4,164 co-op and condominium units, a 12.3% dip from the fourth quarter of 2012, according to Miller Samuel. That’s the lowest inventory level since the firm began tracking the data in 2000. The drop was even more pronounced for new development units, whose availability fell 19.6 percent year-over-year. The situation, however, was much better on the luxury end of the market — the top 10% of all units — where the listing count was 1,190, a 24.9% increase over the same period in 2012.