When Argentina earlier this week appointed its sixth minister of economy in the past six years, it was hard not to conclude that there should be a new economic indicator to measure countries’ reliability: the length of their economy minister’s time in office.

It could be called the “revolving door index,” and it would be listed alongside growth, inflation, exports and imports in the tables of economic data put out by the World Bank and other international institutions.

By the proposed measuring tool, many Latin American countries would fare pretty badly.

Consider:

• In Argentina, the six economy ministers who have held the job since former President Nestor Kirchner — who by most accounts is still the real power behind the presidency — took office in May 2003 are Roberto Lavagna, Felisa Miceli, Miguel Peirano, Martin Lousteau, Carlos Fernandez and — since Tuesday — Amado Boudou. Average time in office: 12 months.

• In Ecuador, since President Rafael Correa took office in January 2007, there have been four economy ministers: Fausto Ortiz, Magdalena Barreiro, Vilma Salgado and Elsa Viteri. Average time in office: seven months.

• In Venezuela, there have been nine changes in the Finance Ministry — the key economic policy job in the country — since President Hugo Chavez took office in 1998. Chavez’s first finance minister was Maritza Izaguirre, followed by Jose A. Rojas, Gen. Francisco Uson, Nelson Merentes, Tobias Nobrega, a new term by Nelson Merentes, Rodrigo Cabeza, Rafael Isea Romero and Ali Rodriguez. Average time in office: 14 months.

Claudio Loser, an analyst with the Inter-American Dialogue think tank in Washington and former head of the International Monetary Fund’s Western Hemisphere department, told me that he likes the idea of creating a “revolving door” index.

All too often, when things go bad, presidents fire their economy ministers instead of correcting bad economic policies, he said.

“It’s a reflection of the little importance economy ministers have in many of these countries,” Loser says. “Presidents appoint weak economy ministers, and when the ministers tell them they have to cut spending, they are fired.”

Writing in Argentina’s daily La Nacion, economist Roberto Cachanosky said Wednesday, “The bottom line is that there is no economist who could solve a crisis like that of Argentina, suffering from inflation plus recession, if there is no government behind him or her that generates confidence.”

It may be no coincidence that a recent report by the United Nations Economic Commission for Latin America and the Caribbean (ECLAC) predicted a 40 percent drop in foreign investments in Latin America this year. The decline is largely due to the global economic crisis, but could be mitigated in several countries if investors were offered a greater degree of stability, economists say.

The good news is that several other Latin American countries have had relatively few economy ministers in recent years.

Chile, where the job of running the country’s economy is held by the Finance Ministry, President Michelle Bachelet, has only one finance minister — Andres Velasco — since she took office in March 2006.

In Brazil, where the Finance Ministry is also in charge of key economic policies, there have been only two finance ministers — Antonio Palocci and Guido Mantega — since President Luiz Inacio Lula da Silva took office in January 2003. Colombia has had three finance ministers — Roberto Junguito, Alberto Carrasquilla and Oscar I. Zuloaga — since President Alvaro Uribe took office in August 2002.

My opinion: It’s not surprising that, according to ECLAC figures, 80 percent of all foreign direct investments to South America last year went to three countries — Chile, Brazil and Colombia. They are among the countries that have had the fewest changes in their economy and finance ministries.

Granted, there may be other factors, but the fact that the bulk of foreign investment to the region is going to the countries with the least rotation in their economic ministries is pretty telling.

The “revolving door index” is definitely in the minds of investors, even if they don’t know it as such.