| 年月 | 单位：% |
| 2010-12 | 19.70 |
| 2010-11 | 19.40 |
| 2010-10 | 21.20 |
| 2010-09 | 19.60 |
| 2010-08 | 19.50 |
| 2010-07 | 18.60 |
| 2010-06 | 19.20 |
| 2010-05 | 19.20 |
| 2010-04 | 20.60 |
| 2010-03 | 20.40 |
| 2010-02 | 20.60 |
| 2009-12 | 19.40 |
| 2009-11 | 19.90 |
| 2009-10 | 19.90 |
| 2009-09 | 19.00 |
| 2009-08 | 20.20 |
| 2009-07 | 20.90 |
| 2009-06 | 19.20 |
| 2009-05 | 17.80 |
| 2009-04 | 16.90 |
| 2009-03 | 18.90 |
| 2009-02 | 10.00 |
| 2008-12 | 19.70 |
| 2008-11 | 22.70 |
| 2008-10 | 22.80 |
| 2008-09 | 29.10 |
| 2008-08 | 24.10 |
| 2008-07 | 24.50 |
| 2008-06 | 23.60 |
| 2008-05 | 22.80 |
| 2008-04 | 19.90 |
| 2008-03 | 22.70 |
| 2008-02 | 17.10 |
| 2007-12 | 20.60 |
| 2007-10 | 18.70 |
| 2007-09 | 17.70 |
| 2007-07 | 15.60 |
| 2007-06 | 14.30 |
| 2007-05 | 19.10 |
| 2007-04 | 15.70 |
| 2007-03 | 14.30 |
| 2007-02 | 27.10 |
| 2006-12 | 15.30 |
| 2006-11 | 14.90 |
| 2006-08 | 13.00 |
| 2006-07 | 13.30 |
| 2006-06 | 15.70 |
| 2006-05 | 14.50 |
| 2006-04 | 12.50 |
| 2006-03 | 13.70 |
前瞻产业研究院 咨询·服务