| Year | Illiteracy | Elementary | Junior | High | College | Undergraduate | Graduate |
| Contribution rate | |||||||
| 2002 | −0.46% | −2.94% | 18.35% | 14.34% | 5.11% | 2.68% | 0.64% |
| 2003 | 1.00% | 8.28% | 3.05% | 1.44% | 3.81% | −0.34% | −0.14% |
| 2004 | −1.44% | −0.81% | 14.50% | 2.54% | 0.04% | 1.08% | −0.05% |
| 2005 | 2.48% | −2.89% | 14.45% | 3.90% | −0.02% | 1.07% | 0.60% |
| 2006 | −2.35% | 13.29% | 4.06% | 0.56% | −1.23% | −0.38% | 0.56% |
| 2007 | −2.55% | −8.15% | 6.67% | 1.13% | 2.98% | 2.57% | 0.11% |
| 2008 | 1.67% | −5.19% | −1.34% | 4.20% | 1.57% | 1.65% | 0.00% |
| 2009 | 0.35% | 5.06% | 22.83% | 13.91% | −1.47% | −1.35% | 0.44% |
| 2010 | −1.13% | −6.93% | 6.16% | 2.16% | 5.89% | 5.74% | 0.10% |
| 2011 | −0.71% | −3.70% | 7.03% | 19.72% | 6.89% | 2.41% | 0.29% |
| 2012 | −0.99% | −3.63% | 380.99% | 118.70% | 5.14% | 6.83% | 5.65% |
| 2013 | −0.42% | 3.67% | 26.36% | 1.88% | 3.31% | 10.13% | 0.94% |
| 2014 | −1.10% | −6.69% | 3.62% | 16.17% | 10.29% | −0.82% | 0.13% |
| 2015 | 9.39% | −0.17% | −44.00% | 2.63% | 19.34% | 14.61% | 0.53% |
| Mean | 0.27% | −0.77% | 33.05% | 14.52% | 4.40% | 3.28% | 0.70% |