XSL count number of nodes with parameter

I have the following xml :

 <pax>
     <age>5</age>
 </pax>
  <pax>
     <age>5</age>
 </pax>
  <pax>
     <age>12</age>
 </pax>

And the follwoing xslt:

 <xsl:for-each select="paxes/pax">
                <xsl:variable name="PaxAge" select="age"/>
                <COUNT>
                  <xsl:value-of select='count(paxes/pax/age[text()=$PaxAge])'/>
                </COUNT>
   </xsl:for-each>

However the result I get in count is always

<COUNT>1</COUNT>
<COUNT>1</COUNT>
<COUNT>1</COUNT>

If I change it to

<xsl:value-of select='count(paxes/pax/age[text()="5"])'/>

I will receive

<COUNT>2</COUNT>
<COUNT>2</COUNT>
<COUNT>2</COUNT>

How can I get the write count for each iterate?