| Year | Illiteracy | Elementary | Junior | High | College | Undergraduate | Graduate |
| Contribution rate | |||||||
| 2002 | −0.93% | −5.26% | 13.75% | 17.64% | 4.52% | 4.60% | 1.80% |
| 2003 | 1.47% | 8.47% | 7.04% | −0.02% | 4.04% | −0.65% | −0.17% |
| 2004 | −0.30% | 1.73% | 16.32% | 4.56% | 0.83% | −0.17% | 0.10% |
| 2005 | −0.16% | −3.69% | 0.82% | 4.57% | −0.27% | 1.93% | 0.26% |
| 2006 | 0.97% | 2.58% | 23.45% | −4.91% | −2.44% | 2.02% | 0.74% |
| 2007 | −0.78% | −4.60% | 9.53% | 9.42% | 1.76% | 0.75% | 0.02% |
| 2008 | −0.58% | 4.73% | 12.87% | 6.38% | 3.25% | 4.00% | −0.04% |
| 2009 | 0.58% | 1.54% | −0.96% | 3.10% | −0.49% | −3.08% | −0.05% |
| 2010 | −0.34% | −3.39% | 16.25% | 6.07% | 5.53% | 6.57% | 0.59% |
| 2011 | 0.56% | −3.33% | −15.23% | 23.56% | 9.55% | 4.38% | −0.45% |
| 2012 | −23.67% | −13.50% | −198.66% | −207.09% | 12.57% | 29.10% | −3.46% |
| 2013 | −0.80% | −0.53% | 2.04% | −11.85% | 8.27% | 6.42% | 1.61% |
| 2014 | 0.05% | −6.71% | −2.99% | 19.96% | 7.47% | 4.17% | −0.28% |
| 2015 | 1.01% | 8.41% | −0.55% | −26.29% | 113.29% | 12.16% | 4.69% |
| Mean | −1.64% | −0.97% | −8.31% | −11.06% | 11.99% | 5.16% | 0.38% |