Reserving concepts an engineer must model, triangles, and why actuarial data needs are not reporting needs.
3 questions in Insurance.
Reserving estimates what business already written will ultimately cost, and pricing needs that cost attributed back to the characteristics that were rated. The loop breaks over which period a loss belongs to, over recent years whose figures are still moving, and over premium earned at rates nobody charges any more.
A loss development triangle groups claims by accident or underwriting period and development age so actuaries can estimate ultimate cost, IBNR and reserve movement. It needs immutable claim transactions, evaluation-date reconstruction and clear paid versus incurred measures.
Reporting shows the current state of each claim, and actuaries need the state as at each past valuation date, cut by accident period and development period. That is a different shape of data, and it cannot be reconstructed from a table that overwrites a claim's figures as it develops.