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:
1973 Mexican legislative election
Table title:
Results
Table:
<table id='hittask' contenteditable='False'>
<tr> <th colspan=1 rowspan=1 > Party </th><th colspan=1 rowspan=1 > Votes </th><th colspan=1 rowspan=1 > % </th><th colspan=1 rowspan=1 > Seats </th><th colspan=1 rowspan=1 > +/- </th></tr>
<tr> <td class="highlighted"  colspan=1 rowspan=1 > Institutional Revolutionary Party </td><td colspan=1 rowspan=1 > 10,458,618 </td><td colspan=1 rowspan=1 > 77.4 </td><td class="highlighted"  colspan=1 rowspan=1 > 189 </td><td colspan=1 rowspan=1 > +11 </td></tr>
<tr> <td colspan=1 rowspan=1 > National Action Party </td><td colspan=1 rowspan=1 > 2,207,069 </td><td colspan=1 rowspan=1 > 16.3 </td><td colspan=1 rowspan=1 > 25 </td><td colspan=1 rowspan=1 > +5 </td></tr>
<tr> <td colspan=1 rowspan=1 > Popular Socialist Party </td><td colspan=1 rowspan=1 > 541,833 </td><td colspan=1 rowspan=1 > 4.0 </td><td colspan=1 rowspan=1 > 10 </td><td colspan=1 rowspan=1 > 0 </td></tr>
<tr> <td colspan=1 rowspan=1 > Authentic Party of the Mexican Revolution </td><td colspan=1 rowspan=1 > 272,339 </td><td colspan=1 rowspan=1 > 2.0 </td><td colspan=1 rowspan=1 > 7 </td><td colspan=1 rowspan=1 > +2 </td></tr>
<tr> <td colspan=1 rowspan=1 > Non-registered candidates </td><td colspan=1 rowspan=1 > 36,858 </td><td colspan=1 rowspan=1 > 0.3 </td><td colspan=1 rowspan=1 > 0 </td><td colspan=1 rowspan=1 > 0 </td></tr>
<tr> <td colspan=1 rowspan=1 > Invalid/blank votes </td><td colspan=1 rowspan=1 > 1,493,267 </td><td colspan=1 rowspan=1 > – </td><td colspan=1 rowspan=1 > – </td><td colspan=1 rowspan=1 > – </td></tr>
<tr> <td colspan=1 rowspan=1 > Total </td><td colspan=1 rowspan=1 > 15,009,984 </td><td colspan=1 rowspan=1 > 100 </td><td class="highlighted"  colspan=1 rowspan=1 > 231 </td><td colspan=1 rowspan=1 > +18 </td></tr>
<tr> <td colspan=5 rowspan=1 > Source: Nohlen </td></tr>
</table>
Question:
What proportion of seats did the Institutional Revolutionary Party win in the 1973 election?
Answer:
The Institutional Revolutionary Party won 189 of the 231 seats.