More realistically, Stoll (1978) and Ho and Stoll (1981, 1983) assume that the dealer is a risk-averse liquidity provider who absorbs temporary imbalances in the order flow. The dealer therefore often holds an inventory of assets that deviates from the desired portfolio position. Since he bears the risk of price fluctuations, the dealer requires compensation in terms of a bid–ask spread. Stoll (1978), Amihud and Mendelson (1980) and Ho and Stoll (1980, 1981, 1983) are the first models that formalize this idea. Biais (1993) also introduces incomplete information about the other dealers’ inventory positions.

In the following section we introduce Stoll’s modelling approach to inventory costs, which considers a one-dealer market, and then extend the model both on the supply side (by introducing a number of competitive dealers) and on the demand side (by allowing for a rational customer who trades both for risk-sharing and to speculate on his private information). The model is then further extended by assuming that liquidity suppliers and liquidity demanders both behave non-competitively and hence take the price impact of their net demand into account.

Here, you will find a cornucopia of places where products in the category you are searching are being sold. The same stores that you have just visited will likely have links on the Internet. So, why bother to go out to the stores in the first place? Because you want to actually see the similar products that are on store shelves. And, you want to gather the information that you can get from the product labels. If you should find a product that is offered for the same purpose as your idea, you can inspect it closely to see if your idea is an improvement on that product. Also, retailers do not usually have every product that is in their stores on their websites, so it is important to make sure that you do not overlook something by failing to make that trip to the store.

Individuals often make and sell products on the Internet that are offered nowhere else. If you neglect to do a good Internet search, you will miss this prior art. What is prior art?

If an active patent covers a product, you cannot legally make and sell it.

If that patent has expired, that product is said to be in the public domain and is now available to anyone to make and sell.

A product that has never been patented but has been offered for sale to the public is also said to be in the public domain and can never be patented.

All of the above examples are prior art; products that have already been presented to the public and cannot now be patent protected. One of the first things the examiners at the patent office will do when they begin with your application is to initiate a thorough search for prior art. If you failed to find these products but they were found in subsequent searches related to your patenting efforts, your patent would be rejected and you would have spent your money and your time in vain. It pays to be meticulous in your Internet  searching.

The rating agencies provide the most accurate data on historical default rates. Based on their data, empirical studies by Wilson  Saunders  and others suggest that default rates tend to be higher in recessionary periods. As might be expected, default rates usually peak at the end of recessions and fall when the economy is expanding. A closer look at history shows that default rates reached their highest levels in the 1930s, peaking at 9 percent in 1932. Since then they have never come close to that level. From 1940 to 1970 they were extremely low, hardly ever exceeding 1 percent. Moody’s themselves note that in the 1973 recession, the default rate was close to zero because only the best issuers had been able to access the capital markets in the previous years. In the early 1990s and at the beginning of the new millennium default rates rose significantly, reaching their peak at about 4 percent. Thus, the default cycle has mirrored the business cycle very well in the past 15 years. Yet one difference is not reflected in this figure. On a dollar-weighted basis, the 2002 default rate for speculative grade issuers was nearly twice as high as in 1991, causing painful losses for many investors.

Furthermore the 2002 default rate for US investment grade issuers reached more than 1 percent on an issuer-weighted basis and almost 3 percent on a dollar-weighted basis. This is substantially above the 30-year average of the investment grade default rate, which is about 25 basis points. Clearly, investment grade defaults are supposed to happen very infrequently.