Now Fisher and his peers praise Mexico for pouring billions of pesos into infrastructure, including ports, railroads, refineries and highways.

In the same breath, investors worry about everything Mexico still needs to do: enforce the rule of law, reduce poverty, bust wasteful telephone and media monopolies, open the national oil industry to foreign investment and curb endemic corruption, the kind that exposed Wal-Mart to allegations the company paid $24 million in bribes to speed permits for construction.

In the World Bank's 2012 annual report “Doing Business,” which measures benchmarks such as enforcing contracts, paying taxes and protecting investors, Mexico finished a middling 53rd among 183 countries, an embarrassing rating for the pro-business government of outgoing President Felipe Calderon.

But the trend lines are up.

“The better off Mexico is, the better off we are,” Fisher said. “And all these Wal-Marts, Sam's Clubs and Costcos are for the emerging middle class.”

Eoin Treacy's view Mexico probably makes more headlines for the ferocity of its drug war than the vibrancy of its middle class or the success of the administration in controlling deficits and inflation. Mexico is one of a number of countries with large young populations and improving governance, albeit from a low base. As such the middle class represents a powerful investment theme for globally oriented companies and investors.

The stock market is one of the best performers globally this year and found support last week in the region of the upper side of the underlying trading range and the 200-day MA. A sustained move below the MA would be required to question medium-term scope for continued upside.

Wal-Mart (2.1%) has at least paused above $70 as it reverts towards the mean by allowing a relatively steady unwind of the overbought condition. While there is still potential for a swifter reversion, a sustained move below the trend mean would be required to question medium-term upside potential.

Costco (1.11%) is becoming increasingly overextended relative to the 200-day MA as it continues to extend its advance. A sustained move below $94 would break the short-term progression of higher reaction lows and suggest a reversion is underway.