个瑞典研究的基础上定量分析，不平衡招标的问题，不能找到关于道路建设。重要的控制变量已被列入，但没有显着的相关性，可以发现在单位价格的偏差和数量的偏差。不平衡投标的实证支持缺乏的原因可能是几个。一个潜在的解释是，承包商没有更多的信息，客户端。这是影响投标的基本假设，这可能不会实现。另一种解释是准备倾斜投标的交易成本。这可能需要对计算机去完成所有的量和发现错估了很长一段时间。这种成本可以延长扭曲的预期利润。也使投标风险大于什么承包商愿意裸。
附原文：
The balance of unbalanced bidding
Johan Nystr?m
Abstract：Based on anecdotal evidence, claims are made that unbalanced bidding is a serious problem in the construction industry. This concept is based on a situation with a contractor being more informed than the client. The asymmetry in information can be used by the contactor to skew unit prices in the ex ante bid and in order to enhance the ex post profit. This is done by increasing the unit price of a quantity that is expected to go up and lower the unit price of a quantity expected to decrease. Research regarding unbalanced bidding has to a large extent focused on models to assists clients in detecting and contractors in optimising the skew. There is also theoretical literature on efficiency losses of unbalanced bidding. The latter models show that it is rational for an informed contractor to raise unit prices on relative underestimated quantities. However, empirical studies that capture the magnitude of the problem are lacking. This paper sets out to fill that void. The analysis is based on a unique dataset of 15 Swedish road investments and 2 795 observations. Data consist of ex ante unit prices and quantities that are related to the final (ex post) quantities. By looking for a positive correlation between these variables and controlling for other affecting variables, the hypothesis of unbalanced bidding can be empirically tested. Along earlier studies on US data, this paper, using more project specific control variables concluded that the effect is even smaller or non-existent.
Keywords:Public procurement; road construction; unbalanced bidding; unit price contracting 1、Introduction
Unbalanced bidding is one potential pitfall of unit price contracting(UPC). If present in a construction project,the concept generates information rents and therefore inefficiencies. This is manifested by the client paying too much for the final product. Unbalanced bidding comes from the contractor being better informed then client (i.e.asymmetric information), which the former uses to their advantage. There is no moral aspect to such a behavior. The contractor acts according to the tendering documents provided by the client. On the contrary, if the contractor were not act on
substandard UPCs then they have to answer to the shareholders of the company the concept is usually portrayed as a big problem in the construction industry. Experts often claim that “this is how it is done in the industry”. This perception is mainly based on anecdotal evidence. Most of the academic papers are theoretical, showing that it is rational for an informed contractor to use unbalanced bidding. There is however a lack of empirical studies supporting these claims and theoretical papers. This paper sets out to empirically determine the problem of unbalanced bidding. The question is whether this pricing strategy exist on the Swedish road construction market A database of 15 Swedish road projects with 2 795 unique observations is used to test the existence of unbalanced bidding. This is the first larger study with a statistical approach that is done in the Nordic countries.
The paper starts with an introduction to the concept of unbalanced bidding, followed by a short review of the academic literature on the concept. Then the introduction continues with the variables and data used to test whether unbalanced bidding exists, followed by the analysis and the conclusions. 2. The concept of unbalance bidding
There are two types of unbalanced bidding discussed in the literature; unbalanced bidding through “front loading” the bids and unbalanced bidding based on information rents regarding quantities. The common denominator is that the contractor is better informed than the client and can use this information to his advantage. Hughes (1982) distinguished the former type of unbalancing as finance cost/cash flow unbalancing in contrast to the error exploitation unbalancing. Cash flow unbalancing involves the contractors marking up prices on quantities that are scheduled for early completion trading off quantities for late completion (Arditi and Chotibhongs, 2009; Skitmoreand Cattell, 2011).
This paper refers to unbalanced bidding based on asymmetric information regarding quantities i.e. Error exploitation. The usual example is taken with a unit price contract (UPC), where the client provides a bill of quantities in the ex ante tendering stage. This in contrast to a Design and Build contract (DB), where the contractor is responsible for both design and construction. Rather than providing a list of quantities of how the e.g. road should be built as in the UPC, the client describes in broad terms what is wanted (simplified, a road from A to B) and let the contractor do the thinking. UPC is still the most common contract in the construction industry.
Assume that there are two inputs to building a road, provision of gravel and pavement. The ex ante bill of quantities for the project estimates 100 m3 of gravel and 150 m2 of pavement. Assume that the contractors differ in costs and information. Contractor 2 exhibits higher marginal costs on both inputs than Contractor 1 but has private information, which Contractor 1 does not. Contractor 1 bids her marginal cost at unit prices of 10. Contractor 2 can then use her superior information regarding the ex post quantities and skew unit prices accordingly. As depicted in table 1, Contractor 2 submits the lower total bid and wins the contract.
3. Research on unbalanced bidding
The earliest papers on unbalanced bidding includes Gates (1967) and Starks (1974), who conceptualized the concept. Since then two branches of theoretical modeling regarding unbalanced bidding have evolved. The first group of models aims at providing practical management for clients to detect (Arditi and Chotibhongs 2009), and for contractors to optimize (Cattell et al. 2010; Cattell et al. 2008; Yizhe and Youjie 1992), unbalanced bidding. These are practical models in order to help practitioners in their day-to-day job with preparing (contractors) and evaluating (clients) bids.
The second type of models are directed towards theoretical audience and has to do with market efficiency. These are typical models in economics, with the purpose of predicting bidding behaviour and thereby socio-economic efficiency. The two most prominent models include Athey and Levin (2001) and Ewerhart and Fieseler (2003). Both models are based on asymmetric information between client and contractor, risk-neutral contractors and end up in corner solutions. This refers to a situation where the contractors hand in zero-unit prices for all quantities but the
mostly underestimated in equilibrium (the example shown in table 3). Mandell and Nystr?m (2014) introduced risk aversion to this model and found an internal solution to the contractors bidding behaviour. This means that the contractor do not skew the bid to the extreme with zero-bids.
Hence, there are rational arguments for an informed contractor to skew the bid. This is not the same as the contractor actually doing it. There are some empirical papers on this matter. Bajari et al (2014) focus on the extent of adaptation costs in road construction but also include data on skewed bids. They find a statically significant result,that a 10 percent quantity overrun will raise the corresponding unit price with 0,5 percent. The authors conclude that unbalanced bidding is not a major determinant in preparing bids. Miller (2014) show that ex post revisions have an effect on the unit prices from subcontractors. The following sections will present and analyse unbalanced bidding in Sweden The data and variables
To approach the empirical question whether unbalanced bidding is a problem, we want to correlate deviations in priced to deviations in quantities with control variables. This paper will be based on data gathered from The Swedish Transport Administration (Trafikverket). The database is based on 15 completed road constructions projects procured by Trafikverket. All data have been collected in the form of the so called MSS-file. This is a standardized excel sheet that all project leaders in Trafikverket use. The excel sheet include all quantities used in a project, both estimated (ex ante) and
final (ex post). Quantitates are defined in different units; meter, square and cubic meters.Trafikverket′s project leaders use this file to fill in quantities throughout the projects. The file also includes unit prices and additional information such as project characteristics, additional orders and changes. From this material we were able to create variables of interest. The deviation in quantities is defined as following way
where, qep are quantities ex post and qeaare ex ante. This gives a normalized measurement of deviation, which is necessary since the units differ between quantities. When no deviations occur, the figure takes on the value zero. The lowest possible figure is -1, which is when estimated quantities has not been used at all. Deviations in unit prices are defined in the same way。 4、Analysis
Based on the data presented above, this paper set out to test the hypothesis that unbalanced bidding exist in Trafikverket’s projects. To confirm the existence of unbalanced bidding, a positive relationship should prevail between deviations in p and deviations in q. This would indicate that contractors raise unit prices on underestimated quantities and lower unit prices on overestimated quantities. The scatter diagram of the observations is presented in Fig. 1.
Fig cannot confirm or reject the hypothesis by the naked eye. The method to test