Economists are forecasting a full recovery from pre-recession levels by 2016 and an expansion of the market by 2020. Despite a slowly growing economy, manufacturers are at record production levels and the surge in auto sales is expected to continue over the next few years. The annual sales rate or SAAR, is estimated to reach 15.4 million this year, climb to 15.9 million in 2015 and hit 16 million in 2017.According to economists at Citigroup, U.S. auto sales are expected to increase sharply in 2015, as drivers continue to replace aging vehicles. The 11.4 year average age of the U.S. fleet is approaching the point where scrap rates begin to skyrocket.According to automotive research firm Polk, leasing now makes up nearly 20% of all new registrations, the highest level in five years, and more than 72% of loans are for 60 months or longer, which keeps monthly payments more affordable for consumers.While auto sales are up, demand from younger buyers, aged 18 to 34, is down as many have trouble finding jobs or have difficulty affording a new vehicle when they are burdened with rising student loan debt, increases in insurance premiums and high gas prices.