"I didn't raise taxes once, I lowered taxes over the last two years."
President Barack Obama, 2.6.11
It would appear the phrase "I didn't raise taxes" would be crystal clear, and certainly when said by the president stated it, everyone could be confident of its meaning. However, this statement must mean something different to Barack Obama.
Americans are aware when the cost of something goes up. When something costs more due to a change in taxes, Americans call this a tax increase. Seems simple enough.