Typically, one would expect the export to contain the equivalent of the Report Preview output. While this is correct for PDF, the CSV export falls back to the initial parameter values defined in the RDL definition, instead of using the actual settings given in Report Preview, e.g. month is always 1, irrespective of what is set in the Report Preview prompts:
<QueryParameters>
<QueryParameter Name="month">
<Value>=Parameters!Month.Value</Value>
</QueryParameter>
<QueryParameter Name="year">
<Value>=Parameters!Year.Value</Value>
</QueryParameter>
<QueryParameter Name="numMonth">
<Value>=Parameters!numMonth.Value</Value>
</QueryParameter>
</QueryParameters>
<ReportParameters>
<ReportParameter Name="Year">
<DataType>Integer</DataType>
<DefaultValue>
<Values>
<Value>2010</Value>
</Values>
</DefaultValue>
<Nullable>false</Nullable>
<AllowBlank>false</AllowBlank>
<MultiValue>false</MultiValue>
<Prompt>Year:</Prompt>
</ReportParameter>
<ReportParameter Name="Month">
<DataType>Integer</DataType>
<DefaultValue>
<Values>
<Value>1</Value>
</Values>
</DefaultValue>
<Nullable>false</Nullable>
<AllowBlank>false</AllowBlank>
<MultiValue>false</MultiValue>
<Prompt>Month:</Prompt>
</ReportParameter>
<ReportParameter Name="numMonth">
<DataType>Integer</DataType>
<DefaultValue>
<Values>
<Value>1</Value>
</Values>
</DefaultValue>
<Nullable>false</Nullable>
<AllowBlank>false</AllowBlank>
<MultiValue>false</MultiValue>
<Prompt>#Months:</Prompt>
</ReportParameter>
</ReportParameters>
The same issue affects the HTML, RTF and XML exports as well.