<p>May 17 (Bloomberg) -- President George W. Bush allowed an increase in oil refinery mergers to go unchecked since he took office and may have contributed to the highest gasoline prices in 20 years as the November election approaches.</p>
<p>The Bush administration approved 33 takeovers totaling $19.5 billion, on top of 21 deals worth $7.3 billion under President Bill Clinton, Bloomberg data shows. Reduced supplies were already pushing up gas prices in Clinton's term, according to a Federal Trade Commission study conducted after pump prices rose to more than $2 a gallon in Milwaukee and Chicago in 2000.</p>