U.S. inventories of propane and propylene reached 97.7 million barrels as of September 11, the highest level in the 22 years that EIA has collected weekly propane inventory statistics. In the first six months of 2015, U.S. propane and propylene inventories were 24.3 million barrels higher on average compared to the same period in 2014. In the past year, nearly all of the increase in inventories occurred in the Gulf Coast region (PADD3).As production of propane and other hydrocarbon gas liquids (HGL) has grown, the ability to transport, store, and export these commodities has expanded. During the first six months of 2015, production of propane at natural gas plants was 31.3 million barrels, or 172,000 barrels per day (b/d), higher than during the first half of 2014. Exports increased by 33.3 million barrels (182,000 b/d) over the same period.