Please read the following table in HTML format from a webpage and then answer the question in detail according to the table. Each table cell is defined by a <td> and a </td> tag. Each table row starts with a <tr> and ends with a </tr> tag. 'rowspan=m' and 'colspan=n' represents a cell spaning over 'm' rows and 'n' columns.

Webpage title:
List of county magistrates of Pingtung
Table title:
Directly elected county magistrates
Table:
<table id='hittask' contenteditable='False'>
<tr> <th colspan=1 rowspan=1 > № </th><th colspan=1 rowspan=1 > Portrait </th><th colspan=1 rowspan=1 > Name (Birth–Death) </th><th colspan=2 rowspan=1 > Term of Office </th><th colspan=1 rowspan=1 > Term </th><th colspan=1 rowspan=1 > Political Party </th></tr>
<tr> <th colspan=1 rowspan=1 > 1 </th><td colspan=1 rowspan=1 > - </td><td colspan=1 rowspan=1 > Chang Shan-chung 張山鐘 Zhāng Shānzhōng (1887–1965) </td><td colspan=1 rowspan=1 > 1 June 1951 </td><td colspan=1 rowspan=1 > 2 June 1954 </td><td colspan=1 rowspan=1 > 1 </td><td colspan=1 rowspan=1 > Kuomintang </td></tr>
<tr> <th colspan=1 rowspan=2 > 2 </th><td colspan=1 rowspan=2 > - </td><td colspan=1 rowspan=2 > Lin Shih-cheng 林石城 Lín Shíchéng </td><td colspan=1 rowspan=1 > 2 June 1954 </td><td colspan=1 rowspan=1 > 2 June 1957 </td><td colspan=1 rowspan=1 > 2 </td><td colspan=1 rowspan=2 > Kuomintang </td></tr>
<tr> <td colspan=1 rowspan=1 > 2 June 1957 </td><td colspan=1 rowspan=1 > 2 June 1960 </td><td colspan=1 rowspan=1 > 3 </td></tr>
<tr> <th colspan=1 rowspan=1 > 3 </th><td colspan=1 rowspan=1 > - </td><td colspan=1 rowspan=1 > Lee Shih-chang 李世昌 Lǐ Shìchāng </td><td colspan=1 rowspan=1 > 2 June 1960 </td><td colspan=1 rowspan=1 > 2 June 1964 </td><td colspan=1 rowspan=1 > 4 </td><td colspan=1 rowspan=1 > Kuomintang </td></tr>
<tr> <th colspan=1 rowspan=2 > 4 </th><td colspan=1 rowspan=2 > - </td><td colspan=1 rowspan=2 > Chang Feng-hsu 張豐緒 Zhāng Fēngxù (1928–2014) </td><td colspan=1 rowspan=1 > 2 June 1964 </td><td colspan=1 rowspan=1 > 2 June 1968 </td><td colspan=1 rowspan=1 > 5 </td><td colspan=1 rowspan=2 > Kuomintang </td></tr>
<tr> <td colspan=1 rowspan=1 > 2 June 1968 </td><td colspan=1 rowspan=1 > 1 February 1973 </td><td colspan=1 rowspan=1 > 6 </td></tr>
<tr> <th colspan=1 rowspan=2 > 5 </th><td colspan=1 rowspan=2 > - </td><td colspan=1 rowspan=2 > Ko Wen-fu 柯文福 Kē Wénfú (1934–2010) </td><td colspan=1 rowspan=1 > 1 February 1973 </td><td colspan=1 rowspan=1 > 20 December 1977 </td><td colspan=1 rowspan=1 > 7 </td><td colspan=1 rowspan=2 > Kuomintang </td></tr>
<tr> <td colspan=1 rowspan=1 > 20 December 1977 </td><td colspan=1 rowspan=1 > 20 December 1981 </td><td colspan=1 rowspan=1 > 8 </td></tr>
<tr> <th colspan=1 rowspan=1 > 6 </th><td colspan=1 rowspan=1 > - </td><td colspan=1 rowspan=1 > Chiou Lien-hui 邱連輝 Qiū Liánhuī (1932–2010) </td><td colspan=1 rowspan=1 > 20 December 1981 </td><td colspan=1 rowspan=1 > 20 December 1985 </td><td colspan=1 rowspan=1 > 9 </td><td colspan=1 rowspan=1 > Independent </td></tr>
<tr> <th colspan=1 rowspan=1 > 7 </th><td colspan=1 rowspan=1 > - </td><td colspan=1 rowspan=1 > Shih Meng-hsiung 施孟雄 Shī Mèngxióng </td><td colspan=1 rowspan=1 > 20 December 1985 </td><td colspan=1 rowspan=1 > 20 December 1989 </td><td colspan=1 rowspan=1 > 10 </td><td colspan=1 rowspan=1 > Kuomintang </td></tr>
<tr> <th colspan=1 rowspan=1 > 8 </th><td colspan=1 rowspan=1 > - </td><td colspan=1 rowspan=1 > Su Tseng-chang 蘇貞昌 Sū Zhēnchāng (1947–) </td><td colspan=1 rowspan=1 > 20 December 1989 </td><td colspan=1 rowspan=1 > 20 December 1993 </td><td colspan=1 rowspan=1 > 11 </td><td colspan=1 rowspan=1 > Democratic Progressive Party </td></tr>
<tr> <th colspan=1 rowspan=1 > 9 </th><td colspan=1 rowspan=1 > - </td><td colspan=1 rowspan=1 > Wu Tse-yuan 伍澤元 Wǔ Zéyuán (1945–2008) </td><td colspan=1 rowspan=1 > 20 December 1993 </td><td colspan=1 rowspan=1 > 14 October 1997 </td><td colspan=1 rowspan=2 > 12 </td><td colspan=1 rowspan=1 > Kuomintang </td></tr>
<tr> <th colspan=1 rowspan=1 >  </th><td colspan=1 rowspan=1 > - </td><td colspan=1 rowspan=1 > Chang Man-chuan 張滿泉 Zhāng Mǎnquán </td><td colspan=1 rowspan=1 > 15 October 1997 </td><td colspan=1 rowspan=1 > 20 December 1997 </td><td colspan=1 rowspan=1 > Kuomintang </td></tr>
<tr> <th colspan=1 rowspan=2 > 10 </th><td colspan=1 rowspan=2 > 蘇嘉全.JPG </td><td colspan=1 rowspan=2 > Su Jia-chyuan 蘇嘉全 Sū Jiāquán (1956–) </td><td colspan=1 rowspan=1 > 20 December 1997 </td><td colspan=1 rowspan=1 > 20 December 2001 </td><td colspan=1 rowspan=1 > 13 </td><td colspan=1 rowspan=2 > Democratic Progressive Party </td></tr>
<tr> <td colspan=1 rowspan=1 > 20 December 2001 </td><td colspan=1 rowspan=1 > 8 April 2004 </td><td colspan=1 rowspan=2 > 14 </td></tr>
<tr> <th colspan=1 rowspan=1 >  </th><td colspan=1 rowspan=1 > - </td><td colspan=1 rowspan=1 > Wu Ying-wen 吳應文 Wú Yìngwén </td><td colspan=1 rowspan=1 > 9 April 2004 </td><td colspan=1 rowspan=1 > 20 December 2005 </td><td colspan=1 rowspan=1 > Democratic Progressive Party </td></tr>
<tr> <th colspan=1 rowspan=2 > 11 </th><td colspan=1 rowspan=2 > - </td><td colspan=1 rowspan=2 > Tsao Chi-hung 曹啟鴻 Cáo Qǐhóng (1948-) </td><td colspan=1 rowspan=1 > 20 December 2005 </td><td colspan=1 rowspan=1 > 20 December 2009 </td><td colspan=1 rowspan=1 > 15 </td><td colspan=1 rowspan=2 > Democratic Progressive Party </td></tr>
<tr> <td colspan=1 rowspan=1 > 20 December 2009 </td><td colspan=1 rowspan=1 > 25 December 2014 </td><td colspan=1 rowspan=1 > 16 </td></tr>
<tr> <th colspan=1 rowspan=2 > 12 </th><td colspan=1 rowspan=2 > - </td><td class="highlighted"  colspan=1 rowspan=2 > Pan Men-an 潘孟安 Pān Mèng'ān (1963-) </td><td class="highlighted"  colspan=1 rowspan=1 > 25 December 2014 </td><td colspan=1 rowspan=1 > 25 December 2018 </td><td colspan=1 rowspan=1 > 17 </td><td colspan=1 rowspan=2 > Democratic Progressive Party </td></tr>
<tr> <td colspan=1 rowspan=1 > 25 December 2018 </td><td class="highlighted"  colspan=1 rowspan=1 > Incumbent </td><td colspan=1 rowspan=1 > 18 </td></tr>
</table>
Question:
Since when has Pan Men-an been the Magistrate of Pingtung County?
Answer:
Pan Men-an has been the Magistrate of Pingtung County since 25 December 2014.