The bid–ask spread is the difference between the price at which liquidity suppliers are willing to sell (ask) and the price at which they are willing to buy (bid). In the theoretical models discussed so far, the existence of the spread is due to the adverse selection costs arising with asymmetric information and to inventory costs. This article concerns the basic empirical models of market microstructure, which take another component of the bid–ask spread into account, namely order processing costs. Order processing costs are the costs associated with the handling of a transaction and are typically modelled as fixed costs per share.

We emphasize that each trade has a buyer and a seller, so the costs for one party are the trading profits for another party. It is natural to look at costs from the perspective of an impatient trader, who consumes liquidity by placing market orders and pays the bid–ask spread. Adverse selection and inventory costs depend on traders’ behaviour, type
and preferences, and on the characteristics of the trading process. By nature, inventory costs exist only in quote-driven markets, where intermediaries have the institutional obligation to supply liquidity continuously; adverse selection and order-processing costs, on the other hand, may exist in any financial market.

If you have done your store and Internet market searches carefully and you have not found your invention, that is an excellent start! Chances are pretty good that your product is not currently being sold. However, you still have a couple of hurdles to get over before you can breathe easily that your idea really belongs to you. According to the United States Patent and Trademark Office (USPTO), over 97% of the patents that are issued to independent inventors never make it to the marketplace! We will talk about this grim statistic in a later chapter and how you can avoid being a part of it. But, what this statistic means is that the patent database is full of patents that have never been seen on store shelves. You will need to make sure that your idea is not one of those that have been patented already.

The United States patent database is huge and complicated, and it would be foolhardy for novice inventors to believe that they could do thorough enough searches to base utility patent applications on them. But, with a little bit of instruction in how to get around on the USPTO website, anyone can do a pretty good preliminary search. What we mean by a preliminary search is this: if you go into the USPTO database and, with a limited amount of searching, you find your invention idea staring back at you; it is time to reassess your idea. Is the prior art (patent) that you just found your exact idea? If it is not, is your idea an improvement over that product? If you believe it to be your exact idea, it is probably best to set it aside and move on to your next idea before you spend any more time or any money on it. But, if you think your idea is significantly different or better, print that patent and take it to a patent agent or attorney for a legal opinion.

If you find a patent that appears to be your exact idea, be sure to read the claims section carefully to make sure that it truly is identical before you abandon your dream. Sometimes two products can be made for the exact same purpose and they can look very similar or even identical in patent drawings and still be very different in the embodiments of how they are actually made.

Considering the importance of dynamic credit risk modeling, the analysis of the relationship between the two major indicators for credit risk, that is default rates and credit spreads, and the business cycle is central for the understanding of the risks associated with investing in corporate bonds. Especially investors that tend to hold securities to maturity, investing in high yield, or running structured portfolios are concerned about avoiding defaults. While default rates generally are a function of the credit cycle outlined above, their current level is not necessarily reflected in credit spreads. In order to judge the attractiveness of the current spreads, one need to not only forecast the future direction of default rates, but also to see whether they are sufficient to cover potential future losses. The sensitivity of the corporate bond market to economic downturns depends particularly on the distribution of the credit quality of the issuers and on the ratio of cyclical companies to noncyclical companies.