Как привязать static ObservableCollection к GridView

Не обновляется UI при изменении коллекции.

Код класса

public static class Contractors
{
    static ObservableCollection<Contractor> ContractorsList;
    public static ObservableCollection<Contractor> CONTRACTORS
    {
        get { return ContractorsList; }
    }
}

Код xaml

<telerik:RadGridView 
 x:Name="contractorsTable" 
 Grid.Row="1" 
 AutoGenerateColumns="False"
 FontSize="12px"
 IsReadOnly="True"
 ShowSearchPanel="True"
        SelectionMode="Extended"
        MouseDoubleClick="ContractorsTable_OnMouseDoubleClick"  
        ItemsSource="{Binding Source={x:Static zaDelo:Contractors.CONTRACTORS}}"
        >
        <telerik:RadGridView.Columns>
            <telerik:GridViewDataColumn DataMemberBinding="{Binding IdContractors}" Header="Код" Width="45" ShowDistinctFilters="False" IsFilterable="False"/>
            <telerik:GridViewDataColumn DataMemberBinding="{Binding Iname}" Header="Наименование" Width="2*" IsFilterable="False"/>
            <telerik:GridViewDataColumn DataMemberBinding="{Binding BidPrice}" Header="Цена" Width="45" IsFilterable="False"/>
            <telerik:GridViewDataColumn DataMemberBinding="{Binding Phone}" Header="Телефон" IsFilterable="False" Width="*" IsSortable="False"/>
            <telerik:GridViewDataColumn DataMemberBinding="{Binding Email}" Header="Email" IsFilterable="False" IsSortable="False" />
            <telerik:GridViewDataColumn DataMemberBinding="{Binding UserName}" Header="ОТВ" Width="50" TextAlignment="Center" IsFilterable="False"/>
            <telerik:GridViewDataColumn DataMemberBinding="{Binding City}" Header="Город" Width="60" IsFilterable="False"/>
            <telerik:GridViewDataColumn DataMemberBinding="{Binding Region}" Header="Район" Width="60" IsFilterable="False"/>
            <telerik:GridViewDataColumn DataMemberBinding="{Binding Loyalty}" Header="Лояльность" Width="60" IsFilterable="False"/>
            <telerik:GridViewDataColumn Header="" CellStyleSelector="{StaticResource ClientBonusS}" Width="15"/>
            <telerik:GridViewDataColumn DataMemberBinding="{Binding IdCart}" Header="Карта" Width="45" TextAlignment="Center" IsFilterable="False"/>
            <telerik:GridViewDataColumn DataMemberBinding="{Binding ContractorGroup}" Header="Назначение" Width="*" IsFilterable="False"/>
        </telerik:RadGridView.Columns>
    </telerik:RadGridView>

Подскажите пожалуйста, как связать что бы обновления в UI было вместе с изменениями в коллекции.