Size information is hard to find, but they are organised and powerful.

(http://www.washingtonpost.com/world/national-security/us-cit...)

$20 billion "flowing back to Mexico".

> One Mexican national-security expert estimated that the [Sinaloa] cartel moves a kilo of cocaine over the U.S. border about every 10 minutes.

(https://en.wikipedia.org/wiki/Mexican_Drug_War#Sinaloa_Carte...)

> Mexico's most-wanted drug trafficker and whose estimated net worth of US$1 billion makes him the 1140th richest man in the world and the 55th most powerful, according to his Forbes magazine profile.

(https://en.wikipedia.org/wiki/Sinaloa_Cartel)

> The United States Intelligence Community considers the Sinaloa Cartel "the most powerful drug trafficking organization in the world" and in 2011, the Los Angeles Times called it as "Mexico's most powerful organized crime group."

(http://www.npr.org/templates/story/story.php?storyId=1031785...)

> Los Zetas — a paramilitary group that acts as enforcers for the Gulf Cartel, the organization of drug gangs that controls narcotrafficking on Mexico's east coast. Many of the Zetas are former Mexican soldiers who were trained to combat drug gangsters. Some of the gunmen are thought to have received training in the United States at the military School of the Americas.

[...]

> The Zetas were among the first criminal groups in Mexico to employ military tactics and heavy weapons, including 50 caliber machine guns, grenade launchers and even ground-to-air missiles.

I am very skeptical of statistics touted by so-called "security experts", spy agencies, or anti-drug organizations like the DEA. They aren't exactly impartial observers, and have every incentive to greatly exaggerate the scale of their opposition. The bigger and meaner their opposition looks, the better the case they can make for increased funding of and attention to their own business.

Unfortunately, the mainstream media usually quotes these biased sources as if they were speaking gospel truth, without a shred of criticism or doubt. These sources are virtually never held to account, asked to justify how they came up with their estimates, or have their estimating methodologies critically scruitinized.

One of the cartel leaders is on Forbe's list of billionaires. They're pretty big.

http://www.forbes.com/profile/joaquin-guzman-loera/

I can't give you any numbers but they have pretty much torn the country apart.

Here's some numbers for what has effectively become a civil war in Mexico: ~55,000 total deaths (16,000 in 2011 alone); nearly 60 journalists killed, over a thousand police and prosecutors killed, nearl a hundred politicians assassinated. Drug revenue in the tens of billions of dollars and somewhere around 100,000 soldiers fighting for the cartels (compared to about 250,000 total soldiers in the Mexican armed forces).

It's an unusual war because the cartels don't care about actually controlling territory too much, they just need to be able to operate, so there are rarely large scale battles between cartel and government soldiers, if the government moves in to some area in force the cartel can just melt away and then hit the government forces opportunistically. Although typically the cartels don't even do that, instead they kill civilians, police, children, and politicians in order to maintain a state of terror and get people to keep their heads down and ignore cartel activity.

Yeah. That's true I know they're big and have a huge effect locally, but scheming to influence lawmaking in another country is pretty big thinking. It's also forward thinking, worrying about your profits 5 years from now.