Rental prices have been skyrocketing in just about every American city. Since the ranks of renters are growing without a corresponding increase in construction, rents are rising across the board. Nationwide, rental prices increased by 3.7 percent from September 2014 to September 2015, according to Zillow. But new analysis shows that the price of housing is increasing a whole lot more for those at the bottom of the economic ladder than for those at the top. A lot more construction is happening at the top of the market, where developers and builders are quickly getting luxury apartments to market. Meanwhile, construction has been slow for cheaper apartments.