As is shown in the chart above,we can see clearly

There are reasons here.Frist,as the job market gets shrinking,but jobs which society provided is limited.Second,it's easy for some students to find work.But the fact is that some students think the salary is so low that they don't want to do the job,they except to find a easy work with a higher salary.Third,with more students get into university,there's no shoreage of a appropriate /suitable employee,so,graduates face fierce competition.