diff --git a/docs/Characteristics.md b/docs/Characteristics.md
index c7c7723..02c2605 100644
--- a/docs/Characteristics.md
+++ b/docs/Characteristics.md
@@ -53,7 +53,9 @@ craneCapacity | Carrying capacity for crane in kg. | positiveDecimal
 elevatorLoad | Maximum elevator load in kg. | positiveDecimal
 floor | Floor number, ground floor is 0, basement floors are negative. | integer
 floorLoad | Maximum floor load in kg/m² | positiveDecimal
-grossPremium | A gross premium is the total premium of an insurance contract before brokerage or | percentdiscounts have been deducted, in percent.
+grossPremium | Current gross return in percentage by reporting date (Net annual rental income x 100 / investment costs) | positiveDecimal
+grossPremiumTarget | Targeted gross return in percentage (Net annual rental income x 100 / investment costs) if fully rented out | positiveDecimal
+netPremium | Current net return in percentage (Net annual rental income - operation and maintenance costs) x 100 / investment costs) | positiveDecimal
 hallHeight | Hall height in m, usually for commercial properties. | positiveDecimal
 hasAttic | Has an attic. | [applicable](#type-applicable)
 hasBalcony | Balcony available. | [applicable](#type-applicable)
diff --git a/schema/schema.xsd b/schema/schema.xsd
index 80695a3..72f9af5 100644
--- a/schema/schema.xsd
+++ b/schema/schema.xsd
@@ -226,7 +226,17 @@
       </xs:element>
       <xs:element name="grossPremium" type="percent" minOccurs="0" maxOccurs="1">
         <xs:annotation>
-          <xs:documentation>A gross premium is the total premium of an insurance contract before brokerage or discounts have been deducted, in percent.</xs:documentation>
+          <xs:documentation>Current gross return in percentage (Net annual rental income x 100 / investment costs)</xs:documentation>
+        </xs:annotation>
+      </xs:element>
+      <xs:element name="grossPremiumTarget" type="percent" minOccurs="0" maxOccurs="1">
+        <xs:annotation>
+          <xs:documentation>Targeted gross return in percentage (Net annual rental income x 100 / investment costs) if fully rented out.</xs:documentation>
+        </xs:annotation>
+      </xs:element>
+      <xs:element name="netPremium" type="percent" minOccurs="0" maxOccurs="1">
+        <xs:annotation>
+          <xs:documentation>Current net return in percentage (Net annual rental income - operation and maintenance costs) x 100 / investment costs).</xs:documentation>
         </xs:annotation>
       </xs:element>
       <xs:element name="hallHeight" type="positiveDecimal" minOccurs="0" maxOccurs="1">