WASHINGTON (AP) — For the first time on record, living with parents is now the most common arrangement for people ages 18 to 34 in the U.S., an analysis of census data by the Pew Research Center has found. Fliers can thank the steep plunge in oil prices since mid-2014 for the drop in prices. [...] the major airlines have announced steps to rein in the oversupply, but such changes can't happen overnight, so fares will remain affordable for the peak travel season. Workplace retirement plans, such as 401(k) accounts, have become a critical retirement savings tool for most Americans. Yet about 40 percent of full-time private sector workers in the U.S.