Nevertheless, incumbent members of Congress running for reelection have strong advantages over challengers. They raise more money because donors fund incumbents over challengers, perceiving the former as more likely to win, and donations are vital for winning elections. One critic compared being elected to Congress to receiving life tenure at a university. Another advantage for representatives is the practice of gerrymandering. After each ten-year census, states are allocated representatives based on population, and officials in power can choose how to draw the congressional district boundaries to support candidates from their party. As a result, reelection rates of members of Congress hover around 90 percent, causing some critics to accuse them of being a privileged class. Academics such as Princeton's Stephen Macedo have proposed solutions to fix gerrymandering in the U.S. Both senators and representatives enjoy free mailing privileges, called franking privileges; while these are not intended for electioneering, this rule is often skirted by borderline election-related mailings during campaigns.