automatic creation of new list from values of old list

one sharepoint list is as follows ListA

colA     colB开发者_Python百科     
Tim      TimA
Tim      TimB
John     JohnA
John     JohnB
Tim      TimC

how can i automatically create a new list using values of ListA ListB

ColAA    ColBB
Tim      3                           ( because there are 3 items for Tim in ListA) 
John     2

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This may not sound proper but the best possible way I see that is to export your lists to excel, do the calculations there and then paste/export the result columns back into a new list in sharepoint. Other than that .NET code or even DataForm XSLT customization (not even considerable due to complexity) for such simple task would be overkill.