A partner's capital account is the essential concept for measuring economic effect, in no small part because a capital account determination is arguably based on fair market value principles. The capital account concept is often in stark contrast to (arguably) more artificial methods of tracking investments, such as the rules that sometimes determine a partner's outside tax basis. For example, in contrast to rules that apply to determination of outside basis, the capital account clearly reflects a partner's economic investment in a partnership in situations involving contributions of built-in gain or built-in loss property to a partnership. Discuss?