Hedgers typically include producers and consumers of a commodity or the owner of an asset or assets subject to certain influences such as an interest rate. For example, in traditional commodity markets, farmers often sell futures contracts for the crops and livestock they produce to guarantee a certain price, making it easier for them to plan. Similarly, livestock producers often purchase futures to cover their feed costs, so that they can plan on a fixed cost for feed. In modern (financial) markets, "producers" of interest rate swaps or equity derivative products will use financial futures or equity index futures to reduce or remove the risk on the swap. Those that buy or sell commodity futures need to be careful. If a company buys contracts hedging against price increases, but in fact the market price of the commodity is substantially lower at time of delivery, they could find themselves disastrously non-competitive (for example see: VeraSun Energy). Investment fund managers at the portfolio and the fund sponsor level can use financial asset futures to manage portfolio interest rate risk, or duration, without making cash purchases or sales using bond futures. Invest firms that receive capital calls or capital inflows in a different currency than their base currency could use currency futures to hedge the currency risk of that inflow in the future. Speculators Speculators typically fall into three categories: position traders, day traders, and swing traders (swing trading), though many hybrid types and unique styles exist. With many investors pouring into the futures markets in recent years controversy has risen about whether speculators are responsible for increased volatility in commodities like oil, and experts are divided on the matter. An example that has both hedge and speculative notions involves a mutual fund or separately managed account whose investment objective is to track the performance of a stock index such as the S&P 500 stock index. The Portfolio manager often "equitizes" unintended cash holdings or cash inflows in an easy and cost effective manner by investing in (opening long) S&P 500 stock index futures. This gains the portfolio exposure to the index which is consistent with the fund or account investment objective without having to buy an appropriate proportion of each of the individual 500 stocks just yet. This also preserves balanced diversification, maintains a higher degree of the percent of assets invested in the market and helps reduce tracking error in the performance of the fund/account. When it is economically feasible (an efficient amount of shares of every individual position within the fund or account can be purchased), the portfolio manager can close the contract and make purchases of each individual stock. The social utility of futures markets is considered to be mainly in the transfer of risk, and increased liquidity between traders with different risk and time preferences, from a hedger to a speculator, for example. Options on futures In many cases, options are traded on futures, sometimes called simply "futures options". A put is the option to sell a futures contract, and a call is the option to buy a futures contract. For both, the option strike price is the specified futures price at which the future is traded if the option is exercised. Futures are often used since they are delta one instruments. Calls and options on futures may be priced similarly to those on traded assets by using an extension of the Black-Scholes formula, namely the Black model. For options on futures, where the premium is not due until unwound, the positions are commonly referred to as a fution, as they act like options, however, they settle like futures.