Inside the grim world of Mexico's drug cartels, the money is good, the risks are great and staff turnover enables a swift ascent through company ranks. A village lookout earns $20 (€16) a day, a campesino preparing product on a Peruvian mountainside, $200 (€160), a truck driver approaching the US border, $2,000 (€1,600), while the jefe (chief) might pocket $2 million (€1.6 million) for each shipment.

All statistics are estimates but piecing together information from trial records and informants, it seems likely that the bigger cartels employ tens of thousands of people and earn billions of dollars each year.

Then there's the violence: Arturo Beltran Leyva began his career with the Sinaloa cartel but then shifted loyalty to the Zetas, a cartel founded by former members of a Mexican special forces unit, Gafe.

Beltran Leyva formed a gang of killers in 2005, seizing control of Guerrero state where 43 students recently disappeared. The job of opening this "franchise" fell to two brothers with ample experience – Alberto and Mario Pineda Villa. They formed a group called Los Pelones (the Bald Ones), quickly becoming key enforcers for the local Guerreros Unidos or United Warriors cartel.

The brothers were killed in 2009 after apparently ripping off their boss. When the boss himself was murdered, the reins of power fell to Cleotilde Toribio Renteria, who in turn was succeeded by an even fiercer killer, Mario Casarrubias Salgado.

In December 2012, Salgado ordered the killing of rival Crisoforo Rogelio Maldonado Jimenez, who was dispatched by a gunman dressed as a doctor using a silencer inside the intensive care unit of a private Mexico City hospital.

That killing in turn unleashed a wave of reprisals which left 70 corpses on the side of the road, halfway between Acapulco and Mexico City. In April, Casarrubias himself was arrested and replaced by his brother Sidronio, the trafficker who allegedly received the 43 students from the local police chief in September, ordered their execution and disposed of their bodies.

Sidronio was detained a month ago. A new enforcer has undoubtedly been appointed and business carries on.

Ten years ago, a handful of jefes controlled half a dozen Mexican cartels which operated across large areas, resolved disputes and earned their money primarily through drugs. The new generation of cartels have splintered and multiplied, operating on a more violent basis over smaller areas, like guerrilla organisations but focused on controlling police and government.

Local journalists call it "the Ebola effect", as the epidemic spreads from villages in Chiapas to Tijuana's urban sprawl, spawning a new term – narcosociety. Lifestyles change overnight. "Everyone knows who is involved," Margarita, a house cleaner from a coastal village in Oaxaca told me, "but everyone is terrified."

The long arm of the cartel is light years more efficient than the rule of law. Drugs are no longer the main business either. Like a company hungry for new revenue streams, the cartels have turned to kidnap and extortion, thriving in areas with a history of weak institutions.

Mexico’s cartels are run by ruthless chief executives who do not pay taxes but do pay off a vast network of private and public officials at federal, state and municipal level on a scale that might well outstrip the country’s effective tax rate.

Mexico's former public security minister Genaro García Luna estimated in 2010 that $1 billion (€805 million) a year was set aside by cartels for that purpose. The return, however, is at least 10 times that, according to the most cautious estimates. In 2008, former president Felipe Calderón's drug tsar, Noe Ramirez, was charged with accepting $450,000 (€362,000) a month from one cartel. Calderón had promised he would be the "president of change". His centre-right National Action Party (Pan), broke the Institutional Revolutionary Party's (PRI) 70-year grip on power in 2000.

Since then Pan’s zeal for tackling corruption has been tempered by bitter experience as an ill-planned campaign against the cartels sparked a major upsurge in violence that has left 100,000 people dead and 25,000 more disappeared. There are no signs of any disruption to the drug trade.

The media has placed great emphasis on the arrest of celebrity traffickers but army and police face allegations of human rights abuses. One recent case, in which army troops killed 22 civilians during a narcotics operation, has raised fresh doubts about the role of the army in fighting drug cartels.

Another consequence of the trade is an increase in rural migration northwards to escape the upsurge in violence. The vulnerable migrants offer cartels yet another opportunity for extortion. For those who remain there is the option of joining armed community patrols seeking to prevent drug gangs from seizing villages and towns.

The government is left with a serious dilemma as it decides whether to disarm the patrols and replace them with more army troops or tolerate the patrols and risk ceding territory to vigilantes. It was widely hoped that when the PRI returned to power in 2012, led by Enrique Peña Nieto, drug violence would decline. The PRI is Mexico’s party of power, its state machinery reaching into every corner of the country, combining repression with populism.

Peña Nieto swiftly brought political rivals on board for a series of economic reforms, the “Pact for Mexico”, while announcing a reduction in drug-related deaths. However the disappearance of the 43 students in September placed Mexico’s cartels and their relationship with state power firmly centre stage.

Peña Nieto was supported by just 38 per cent of voters in the presidential election. He lacks a majority in both houses and faces an opposition mayor in the capital city. His party’s political reforms were approved on the tacit understanding that there would be no raking over the crimes of the past 10 years when the opposition governed.

But the graves keep appearing and relatives besiege officialdom while the media watches and reports. Mexico’s rotten institutions require a radical overhaul that would see government officials, security forces and judicial authorities become servants of the people rather than employees of the cartels.

In the meantime Mexico’s cartel chiefs pay off a new generation of officials as the cash rolls in regardless.