When is a plateau not a plateau? Well, when a market dips at the same time every year for years on end, and then all of sudden it doesn’t, that even keel isn’t mundane at all. Quite the opposite: the absence of winter’s usual decline in rental market activity for luxury rentals in Manhattan couldn’t be more noteworthy. A recent market report showed that rents for Manhattan apartments have been essentially unchanged since October, which means that the usual winter season never materialized. We skipped right over it. Looking back to this time last year, rents are up across the board, especially for two-bedrooms, which is the most distinctive shift. Whereas rent increases in studios apartments in Manhattan led the way in March 2010 and 2011, large apartments are now taking the lead.