Tim Worstall, a fellow at the Adam Smith Institute in London, offers an interesting argument against the movement to raise the U.S. minimum wage to $15 an hour from $7.25 currently.

"A $15 minimum wage would put all workers in the U.S. into the global 1 percent by income," he writes on Forbes.com. "Given that the U.S. labor force is rather larger than merely 1 percent of the global labor force this isn’t really going to work, is it?"

Seattle and Los Angeles already have implemented plans to boost the minimum wage to that level. And companies such as McDonald's and Wal-Mart are lifting their minimum pay too, though not to $15.

Worstall goes further than simply endorsing a $7.25 minimum. "In theory I’m against there being a minimum wage at all," he states. "After all, 96 percent of Americans earn more than the current one so there’s obviously something other than just that minimum wage which causes decent wages to be paid."

Any minimum wage shouldn't exceed 50 percent of median wages, he says.

Speaking of interesting conservative critiques: here's one concerning income inequality from Stephen Moore, a distinguished visiting fellow at The Heritage Foundation.

While President Obama claims that low-income Americans work just as hard as their wealthy counterparts, that simply isn't true, he and Heritage Foundation research associate Joel Griffith write in The Washington Times.

"Yes, many people in poor households heroically work very hard at low wages to take care of their families, no doubt about that," they say.

"Yet the average poor family doesn’t work nearly as much as the rich families do. And that’s a key reason why these households are poor."

Census Bureau data show that for every hour worked by those in a low-income household, those in a wealthy household toil five hours.

"The idea that the rich are idle bondholders who play golf or go to the spa every day while the poor toil isn’t accurate," Moore and Griffith explain.

"The finding that six out 10 poor households have no one working at all is disturbing. Since they have no income from work, is it a surprise they are poor?"

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