India, Feb. 19 -- Yesterday, the shares prices of oil upstream firms like the state-owned ONGC and Oil India slipped by four per cent. The immediate trigger was a slight slide in global crude oil prices, which dipped by a meagre three cents a barrel, or a mere 0.04 per cent. Now, a 0.04 per cent cannot be equated with a four per cent fall, can it? Yet, there is a logic to the market madness. If crude oil prices go down further, it will impact the upstream segment due lower revenues per barrel, tighter margins, lower profits, and reduced expense on future and ongoing exploration projects. The first three will affect the quarterly financials, and the last one will impact earnings in the future. In comparison, lower global oil prices benefit...