This year, more Christmas gifts than usual may still be on their way. According to The Wall Street Journal, UPS, FedEx, and retailers including Amazon, Kohls, Groupon, and Wal-Mart have all been unable to meet promises to deliver packages before the holiday, largely because of an overwhelming and unexpected increase in online shopping. The volume of air packages in the UPS system did exceed capacity as demand was much greater than our forecast, UPS tells the Journal. While online commerce currently accounts for 6 percent of US retail sales, the Journal reports that the National Retail Federation believes it shot up to an average of 14 percent of sales for this years holidays. Making matters worse, the Journal reports that some retailers even pushed back this years deadline for guaranteed delivery by Christmas, making them accountable for even more shipments. Though its not clear exactly how much online shopping increased, but it appears to be a good amount: IBM Digital Analytics reportedly measured a 37 percent increase in online shopping year-over-year for the weekend preceding Christmas, while Forrester Research believes there was a 15 percent increase in online shopping for the holidays — a slight increase over the National Retail Federations estimates.