The Obama administration appears to be deadlocked over what to do in Syria, forcing a policy of inaction, according to a widely circulating New York Times story. But U.S. officials will likely have years more time to debate what to do about Syria's civil war, which could continue into and perhaps through the next presidential administration. According to a review of the political science on the duration of civil wars, Syria's conflict will most likely last through 2020 and perhaps well beyond.

Syria's conflict began with April 2011 protests and subsequent crackdowns. It's not clear the precise moment when it became a civil war, but many media organizations began referring to it as such around early or mid 2012. At most, you might say the war has been waging now for two years. According to studies of intra-state conflicts since 1945, civil wars tend to last an average of about seven to 12 years. That would put the end of the war somewhere between 2018 and 2023.

Worse, those studies have identified several factors that tend to make civil wars last even longer than the average. A number of those factors appear to apply to Syria, suggesting that this war could be an unusually long one. Of course, those are just estimates based on averages; by definition, half of all civil wars are shorter than the median length, and Syria's could be one of them. But, based on the political science, Syria has the right conditions to last through President Obama's tenure and perhaps most or all of his successor's.

Here's what the research shows:

(1) The average civil war was 10 years as of 2002: A 2002 study by James Fearon of Stanford University found the average length of ongoing civil wars to be about 10 years.

(2) That number has probably since increased: The length of civil wars has been increasing steadily since 1945. It hit an all-time high of 15.1 years in 1999, then dropped, perhaps owing to the resolution of conflicts sparked by the end of the Cold War. But it's been ticking back up; the trend suggests that Fearon's 2002 estimate of 10 years would have increased significantly since then. Here's a chart of his data on civil war length:

(3) Civil wars are longer and bloodier than average when foreign powers intervene: A 2008 study by Fearon and David Laitin reaffirmed previous research stating that civil wars tend to be significantly longer when foreign countries intervene decisively on one side. (To be clear, "intervene" here means more than just training a few rebels, as the United States is doing, but to support one faction in outright defeating its enemy.) A 2012 paper reached a similar conclusion, also finding that foreign interventions tends to make all sides more violent and to increase the death toll. Iran is very actively involved in directly aiding Syrian President Bashar al-Assad's forces, as is the Lebanese militant group Hezbollah. Saudi Arabia and other Arab Gulf states are helping to fund and arm rebel groups; foreign jihadist groups are also involved in the fighting, particularly from Iraq.

(4) Civil wars with lots of factions last longer than average. Barbara F. Walter of the University of California at San Diego points to a 2006 paper in the Journal of Political Science arguing that civil wars last longer when there are more competing factions. The number of rebel groups tends to change on a pretty regular basis, but Walter says there are 13. Whatever your count, there are a lot of them, their alliances and allegiances tend to change a lot and, most worrying, they're already fighting one another.

(5) Civil wars are longer than average when no side can disarm the other. It's not just about seizing and holding territory: it's about taking away your opponent's ability to fight you. "Civil wars tend to last a long time when neither side can disarm the other, causing a military stalemate," Fearon concluded in his 2002 study. The Assad regime is actively armed by a foreign power, Iran, which suggests it would be really difficult for the rebels to disarm them. And it's hard to see how Assad could ever disarm the rebels, who come both from within the Syrian population and from across the border in Iraq, given both the popular outrage against his regime and the ease of acquiring weapons.

(6) Civil wars are longer than average when they don't end by negotiated settlement. When Fearon and others calculated the average length of civil wars, the lower end of their data was filled with countries that achieved peace through a negotiated settlement, also known as a peace deal. Walter says the odds of this happening are "probably close to zero." She explains that the research finds you need two things for a negotiated settlement: a third party willing to commit resources such as peacekeepers and an "divide political power amongst the combatants based on their position on the battlefield." Syria has neither. She adds that only one in four civil wars ends in negotiated settlement; most end in outright victory, which is made less likely by foreign intervention, as the foreign powers can keep supplying arms and money long after the stalemate would have otherwise exhausted both sides.

You don't need all this research to see that, two years into Syria's civil war, there's no sign that the conflict is headed anywhere toward resolution. Syrian territory is split between regime forces, Arab rebels and Kurdish groups, all of whom appear deadlocked. Rebel factions are dividing and fighting among one another. Food insecurity is becoming a greater problem, as is access to medical care. Other Middle Eastern states are getting more involved, turning Syria into a proxy war between Iran and Arab Gulf states. And while Syria did agree to give up its chemical weapons, Russia is otherwise shielding the regime from much international action.

That the research above seems to point to at least another 10 years is hardly surprising, particularly when we look at similar conflicts. Neighboring Lebanon had a civil war, also with sectarian divisions and foreign interventions, that lasted either 15 or 30 years, depending on how you count it. An even greater risk might be Syria's conflict following a model like Afghanistan's, which had its 1980s war followed by another civil war, in the 1990s, between the victorious rebel groups; Syria's rebels are already fighting one another, leading to fears that a rebel victory would spark a second war.

Ten years, or 15 or however long it might be, is a very long time. It's not just that President Obama is likely to leave office with the war unsolved. His successor could serve most or all of two full terms while the killing continues. The next president could be winding down his or her second term, in 2023, with the war still raging, still unsolved. It's already killed over 100,000 Syrians and displaced over 1 million. There's no telling what it would cost after a full decade.