Select Box Always has selected value twice

I have a select box consisting of years and the selected year always appears twice - the select box is being populated from a List of Strings and there are no duplicates in the list the following is an example any idea why the selected year always appears twice

<td align="center">Calendar Year : <img src="public/images/red_arrow_compulsary_field.gif" border="0">
            <select name="selectYear" id="selectYear" style="width:100px" onchange="javascript:onChangeCalendarYear();">
    <option value="-1"
    > 2011</option>
    <option value="1991">1991</option>
    <option value="1992">1992</option>
    <option value="1993">1993</option>
    <option value="1994">1994</option>
    <option value="1995">1995</option>
    <option value="1996">1996</option>
    <option value="1997">1997</option>
    <option value="1998">1998</option>
    <option value="1999">1999</option>
    <option value="2000">2000</option>
    <option value="2001">2001</option>
    <option value="2002">2002</option>
    <option value="2003">2003</option>
    <option value="2004">2004</option>
    <option value="2005">2005</option>
    <option value="2006">2006</option>
    <option value="2007">2007</option>
    <option value="2008">2008</option>
    <option value="2009">2009</option>
    <option value="2010">2010</option>
    <option value="2011">2011</option>
    <option value="2012">2012</option>
    <option value="2013">2013</option>
    <option value="2014">2014</option>
    <option value="2015">2015</option>
    <option value="2016">2016</option>
    <option value="2017">2017</option>
    <option value="2018">2018</option>
    <option value="2019">2019</option>
    <option value="2020">2020</option>
    <option value="2021">2021</option>
    <option value="2022">2022</option>
    <option value="2023">2023</option>
    <option value="2024">2024</option>
    <option value="2025">2025</option>
    <option value="2026">2026</option>
    <option value="2027">2027</option>
    <option value="2028">2028</option>
    <option value="2029">2029</option>
    <option value="2030">2030</option>
    <option value="2031">2031</option>