XSD does not output a "Union" SimpleType

[Codex Twin]

hello group:

The following is a fragment from a schema which defines the
EWethnicCategor yStructure type. As you can see, its type is defined by the
SimpleType enumeration EWethnicCategor yType.
EWethnicCategor yType is defined as a union with the CommonEthnicCat egoryType
SimpleType enumeration.

Now when I use the XSD tool to create a C# class of this schema, the
resulting code does not include the SelectedEthnicC ategory enumeration.
However, when I change its type to CommonEthnicCat egoryType, I at least get
the CommonEthnicCat egoryType enumeration.

What is going wrong?
What do I need to output the entire union defined by EWethnicCategor yType?

Thanks

=============== =============== =============== =============== ============

<xsd:element name="EWethnicC ategory" type="EWethnicC ategoryStructur e"/>
<xsd:complexTyp e name="EWethnicC ategoryStructur e">
<xsd:sequence >
<xsd:element name="SelectedE thnicCategory" type="EWethnicC ategoryType">
<xsd:annotation >
<xsd:documentat ion>The Ethnic category selected from the available
list</xsd:documentati on>
</xsd:annotation>
</xsd:element>
<xsd:element ref="OtherSpeci fiedEthnicCateg ory" minOccurs="0"/>
</xsd:sequence>
</xsd:complexType >
<xsd:element name="OtherSpec ifiedEthnicCate gory"
type="core:Popu latedStringType ">
</xsd:element>
<xsd:simpleTy pe name="EWethnicC ategoryType">
<xsd:union memberTypes="Co mmonEthnicCateg oryType">
<xsd:simpleType >
<xsd:restrictio n base="xsd:strin g">
<xsd:enumeratio n value="British"/>
</xsd:restriction >
</xsd:simpleType>
</xsd:union>
</xsd:simpleType>
<xsd:simpleTy pe name="CommonEth nicCategoryType ">
<xsd:annotation >
<xsd:documentat ion>Ethnic categories used by all areas (except Northern
Ireland which has completely different list)</xsd:documentati on>
</xsd:annotation>
<xsd:restrictio n base="xsd:strin g">
<xsd:enumeratio n value="Irish"/>
<xsd:enumeratio n value="Other White"/>
<xsd:enumeratio n value="White &amp; Black Caribbean"/>
<xsd:enumeratio n value="White &amp; Black African"/>
<xsd:enumeratio n value="White &amp; Asian"/>
<xsd:enumeratio n value="Other Mixed"/>
<xsd:enumeratio n value="Indian"/>
<xsd:enumeratio n value="Pakistan i"/>
<xsd:enumeratio n value="Banglade shi"/>
<xsd:enumeratio n value="Other Asian"/>
<xsd:enumeratio n value="Caribbea n"/>
<xsd:enumeratio n value="African"/>
<xsd:enumeratio n value="Other Black"/>
<xsd:enumeratio n value="Chinese"/>
<xsd:enumeratio n value="Any Other"/>
<xsd:enumeratio n value="NOT STATED"/>
</xsd:restriction >
</xsd:simpleType>