"The developments are alarming," Peter Nordlund, an economist with the Swedish Defence Research Agency (FOI) told the Svenska Dagbladet (SvD) newspaper.
In 2013, 3,784 people started basic training with the Swedish Armed Forces. Recruitment plans forecast that eight of ten soldiers who complete basic training would continue as employees of the military.
But in reality, only six of ten who started basic training continue with careers in the military.
Moreover, soldiers who continue after basic training are supposed to remain under contract for six years. But during 2013, 14 percent of Sweden's newly-minted soldiers quit before their contracts were up.
If such attrition rates hold, that means only 23 percent of soldiers will complete their six-year contracts.
"The results so far are worse than the worst case scenarios we calculated when the system was created," Nordlund said in reference to Sweden's 2010 transition from conscription to an all-volunteer military.
"Back in 2010, we began thinking about a Plan B if the new system didn't develop according to plan. It may be time for Plan B now."
In order to fill in the gaps left by soldiers who quit, Sweden needs 7,000 to 8,000 people to sign up for basic training, more than twice the current enrollment.
That would mean seven percent of a given age group would have to volunteer to join the military, Nordlund explained.
"Not even the United States, which spends a lot of money on recruitment, has recruiting figures higher than six percent," he told SvD.
Getting more people to sign up for basic training would also mean a 600 to 800 million kronor ($92 to 123 million) increase in annual recruiting costs, he added.