| Year | Rate | Ratio |
|---|
| * 2002 | 2.37 | 100 |
| 2003 | 2.52 | 100 |
| 2004 | 2.62 | 90.14 |
| 2005 | 2.72 | 81.76 |
| 2006 | 2.78 | 75.31 |
| 2007 | 2.87 | 68.29 |
| 2008 | 2.984 | 65.45 |
| 2009 | 3.124 | 65.02 |
| 2010 | 3.271 | 67.79 |
| 2011 | 3.514 | 67.93 |
| 2012 | 3.654 | 69.55 |
| 2013 | 3.745 | 71.08 |
| 2014 | 3.826 | 74.49 |
| 2015 | 3.889 | 74.65 |
| * 2016 | 3.127 | 100 |
| 2017 | 3.202 | 96.53 |
| 2018 | 3.242 | 95.81 |
| 2019 | 3.312 | 93.39 |
| 2020 | 3.40 | 91.14 |
| 2021 |
| 92.02 |
* Denotes revaluation year