.More recently, the continued growth of online shopping, combined with increasing awareness of the role transportation (including package delivery) has on the environment, has contributed to the rise of emerging competition from niche carriers or rebranded incumbents. For instance, the US Postal Service claims "greener delivery" of parcels on the assumption that USPS letter carriers deliver to each US address, six days a week anyway, and therefore offer the industry's lowest fuel consumption per delivery. Other carriers, like ParcelPool.com,[11 (Unknown or private posting)] which specializes in residential package delivery to APO-FPO addresses, Hawaii, Alaska, Puerto Rico and other US Territories, arose in response to increased demand from catalog retailers and online e-tailers for low-cost residential delivery services closely matching service standards normally associated with more expensive expedited parcel delivery.