Three weeks ago, fast-food workers across the United States went on strike to protest the country's minimum wage of $7.25 an hour.

The protesters called for a more-than-doubled minimum wage of $15 an hour.

In a note to clients today, ConvergEx Group strategists look at minimum wages around the world.

"Out of the 20 or so countries listed on The Economist's Big Mac Index (countries that also have minimum wages – Italy and Germany do not, for example) from 2012, the U.S. has the 7th highest minimum wage on an absolute basis, about the median number," say the strategists. "The absolute lowest federal minimum wage is in Sierra Leone, where workers can expect just $0.03/hour. India is the lowest among larger economies with a $0.28/hour rate. Australia is at the opposite end of the spectrum, with a whopping $16.88 hourly mandated wage."

If the minimum wage in the United States were to increase to $15, as U.S. fast-food workers proposed, the country's minimum wage would be second only to Australia's.

The ConvergEx strategists also calculated the number of minutes of working the minimum wage it takes to buy a Big Mac in countries around the world. Click here to see those results »

minimum wages around the worldBusiness Insider/Matthew Boesler, data from ConvergEx Group