Unbalanced Highway Contract Tendering

This paper deals with a central and recurrent concern of managers responsible for highway tendering: formulating unit bids for Unit Price Proposals. Unit Price Proposals are prepared by the client and indicate contract items and (estimated) quantities deemed necessary to accomplish the proposal objective. The bidder is required to indicate unit prices or bids. These unit bids are multiplied by the indicated quantities and summed to arrive at the bid total. Virtually every tender (bid) is unbalanced in order to improve cash flow. Often the unbalancing is neither competent nor conscious. A linear programming model was devised to determine unit bids that maximize the present worth of future profit. The model characterizes the managerial environment with uncommon competence. Examples illustrate features of implementation. The model is especially useful for large and complicated contracts of long duration. These linear models have the remarkable feature that, for given project information, no other means of unbalancing will yield a greater present worth.     

Allocation of School Bus Contracts By Integer Programming

When public transport is put out to tender, the task of allocating contracts to operators can be far from trivial. In addition to vehicle constraints, there can be group bids wherein a discount is offered for certain contracts in combination. An efficient integer programming formulation is presented which is then used to solve a large-scale real-life example.     

Recurrent Competitive Bidding

A competitive bidding policy can be formulated if prior probability distributions of competitors' bids for future contracts have been determined. A method for determining these prior probability distributions is described for markets where there are a large number of customers. The identity of each winning company and its bid are assumed to be available to competitors and other customers so that the market reacts quickly to changes. A real example of the use of the method is given. The suppliers' general levels of bidding and their variation with individual types of customer are evaluated quantitatively. The results are consistent with qualitative knowledge of the market.     

Simple probability models for project contracting

There are two aspects to the process of price setting using sealed bids. The project owner is interested in deploying the contract mechanism that will secure reliable service at the cheapest cost. On the other hand, each contractor bidding for the project is interested in winning the contract but at a price that assures him a reasonable profit margin. We use a parsimonious stochastic model to compare and contrast some commonly used contracts from the point of view of the project owner. We show that if the bidders are risk neutral, a Fixed Price contract results in the smallest expected procurement cost for the project owner. We introduce and analyze Menu contracts and show that the expected price of a Menu contract lies in between the prices of the Fixed Price and Cost Plus contracts for the same project. We analyze how risk aversion and collusion, which we model using concepts of stochastic dependence, impacts the average winning bid price.     

Competitive Tendering Strategies in the Bus Industry

School bus services within the UK are subsidised by the local Passenger Transport Executive and bus operators tender for the contracts, with the lowest price normally winning. Analysis of the bids in one district showed that the companies had pricing strategies, which could be estimated from freely available data when they were simple. The difficulties arose when competitors segmented the market.     

建筑业中投标合同的统计和模糊分析

许多货物和劳务合同是依据密标的拍卖签订的。在建筑业中，有报价选择特权的承包商决定工程的标价常常是一个艰难的过程。一般公认的标价办法是实际成本加毛利。本文运用主因素分析法和回归分析法来研究香港的竞争性承包商的投标成效，同时也用模糊线性回归来研究投标过程的结构。最后，根据香港建筑业投标数据库，比较了统计和模糊回归分析这两种方法的结果。     

The full-information best-choice problem with uniform or gamma horizons

A decision-maker has to choose one from among a Poisson stream of i.i.d. bids, with no recall. The stream stops at a random time with a uniform (in the first case) or Erlang (in the second case) distribution. We solve the problem explicitly for maximal expected gain for bids that may take on any finite number of values. A fast procedure to solve the problem for fixed horizon is presented as well.     

Nash equilibrium in a pay-as-bid electricity market Part 2 - best response of a producer

We consider a multi-leader-common-follower model of a pay-as-bid electricity market in which the producers provide the regulator with either linear or quadratic bids. We prove that for a given producer only linear bids can maximize his profit. Such linear bids are referred as the ‘best response’ of the given producer. They are obtained assuming the demand is known and some estimate of the bids of the other producers is available. Nevertheless we also show that whenever no best response exists, the optimal profit can be asymptotically attained by a sequence of quadratic bids converging to the so-called ‘limiting best response’. An explicit formula for such a sequence is provided.     

A multistage exchange trading model with asymmetric information and elements of bargaining

A modification of the discrete multistage exchange trading model with risky securities is considered. At each stage of trading, the players place their integer bids. One of the players knows the real price, while the other knows only its probability distribution. The transaction price is defined as a convex combination of the proposed bids with some given coefficient. The solution to an infinitely long game is obtained.     

On being balanced in an unbalanced world

This paper examines the case of a procurement auction for a single project, in which the breakdown of the winning bid into its component items determines the value of payments subsequently made to bidder as the work progresses. Unbalanced bidding, or bid skewing, involves the uneven distribution of mark-up among the component items in such a way as to attempt to derive increased benefit to the unbalancer but without involving any change in the total bid. One form of unbalanced bidding for example, termed Front Loading (FL), is thought to be widespread in practice. This involves overpricing the work items that occur early in the project and underpricing the work items that occur later in the project in order to enhance the bidder's cash flow. Naturally, auctioners attempt to protect themselves from the effects of unbalancing—typically reserving the right to reject a bid that has been detected as unbalanced. As a result, models have been developed to both unbalance bids and detect unbalanced bids but virtually nothing is known of their use, success or otherwise. This is of particular concern for the detection methods as, without testing, there is no way of knowing the extent to which unbalanced bids are remaining undetected or balanced bids are being falsely detected as unbalanced. This paper reports on a simulation study aimed at demonstrating the likely effects of unbalanced bid detection models in a deterministic environment involving FL unbalancing in a Texas DOT detection setting, in which bids are deemed to be unbalanced if an item exceeds a maximum (or fails to reach a minimum) ‘cut-off’ value determined by the Texas method. A proportion of bids are automatically and maximally unbalanced over a long series of simulated contract projects and the profits and detection rates of both the balancers and unbalancers are compared. The results show that, as expected, the balanced bids are often incorrectly detected as unbalanced, with the rate of (mis)detection increasing with the proportion of FL bidders in the auction. It is also shown that, while the profit for balanced bidders remains the same irrespective of the number of FL bidders involved, the FL bidder's profit increases with the greater proportion of FL bidders present in the auction. Sensitivity tests show the results to be generally robust, with (mis)detection rates increasing further when there are fewer bidders in the auction and when more data are averaged to determine the baseline value, but being smaller or larger with increased cut-off values and increased cost and estimate variability depending on the number of FL bidders involved. The FL bidder's expected benefit from unbalancing, on the other hand, increases, when there are fewer bidders in the auction. It also increases when the cut-off rate and discount rate is increased, when there is less variability in the costs and their estimates, and when less data are used in setting the baseline values.     

Optimal bidding in auctions of mixed populations of bidders

A mixed population of bidders consists of two asymmetric groups. Members of the first group are game-theoretic players, who maximize their expected profit and incorrectly believe that their opponents act similarly. The second group of bidders adopts an irrational strategy: they either choose their bids randomly following a given probability distribution, in a “naïve” form of bidding, or follow a decision-theoretic approach, maximizing their expected profit under the assumption that all other bids are random. In a sealed bid private-value procurement auction we examine the optimal strategy of a new player, who has perfect knowledge of the structure of the mixed bidder population and enters the auction. The optimal bid of the new bidder is derived when the cost and mark-up follow a uniform distribution in [0, 1]. The effect of the relative size of the group of game-theoretic bidders and the population size on the optimal bid price is established.     

常数相对风险厌恶多单位拍卖的比较静态与定价结构

考虑竞价者具有常数相对风险厌恶时的多单位拍卖问题,讨论均衡出价与风险偏好以及价值分布之间的关系.在竞价者具有相同的风险偏好的对称拍卖情形,利用风险中性等价导出了比较静态的充要条件,这一充要条件综合了风险偏好和价值分布的变化.在竞价者具有不同的风险偏好的非对称拍卖中,导出了均衡出价关于风险偏好的线性定价结构,依据这一结构,对任意给定出价,竞价者要求的剩余是其风险厌恶参数的线性函数,并且可以分解为竞争性剩余和风险厌恶剩余.     

Compact bidding languages and supplier selection for markets with economies of scale and scope

Combinatorial auctions have been used in procurement markets with economies of scope. Preference elicitation is already a problem in single-unit combinatorial auctions, but it becomes prohibitive even for small instances of multi-unit combinatorial auctions, as suppliers cannot be expected to enumerate a sufficient number of bids that would allow an auctioneer to find the efficient allocation. Auction design for markets with economies of scale and scope are much less well understood. They require more compact and yet expressive bidding languages, and the supplier selection typically is a hard computational problem. In this paper, we propose a compact bidding language to express the characteristics of a supplier’s cost function in markets with economies of scale and scope. Bidders in these auctions can specify various discounts and markups on overall spend on all items or selected item sets, and specify complex conditions for these pricing rules. We propose an optimization formulation to solve the resulting supplier selection problem and provide an extensive experimental evaluation. We also discuss the impact of different language features on the computational effort, on total spend, and the knowledge representation of the bids. Interestingly, while in most settings volume discount bids can lead to significant cost savings, some types of volume discount bids can be worse than split-award auctions in simple settings.     

Optimal contracts in portfolio delegation

The optimal contracts in portfolio delegation under general preferences are characterized when the underlying state variable is not contractible, and the principal must rely on the final returns of portfolios to design the compensation schemes for the fund manager. We show that the optimal contracts satisfy a second-order nonlinear ordinary differential equation that depends on the utility functions and the distribution of state price density. In general, there is an efficiency loss for the optimal contracts unless the utility functions of both the principal and the agent exhibit linear risk tolerance with identical cautiousness. Additional contractible observables, like stock indexes, can be used to improve the efficiency of the second-best contracts, even if they are not perfectly correlated with the underlying state price. A continuous-time example with power utilities is presented to illustrate the features of the optimal contracts.     

Home-grown values and incentive compatible auction design

The behavioral properties of several auctions designed to elicit individual valuations for an object are studied using controlled laboratory experiments. Our experiments lead us to conclude that there are some behavioral differences between alternative incentive-compatible institutions for eliciting home-grown values, contrary to the theoretical expectation that these institutions are isomorphic. These results are consistent with earlier experimental results using induced values. The most important finding is that English auctions appear to elicit lower bids than Vickrey auctions, after controlling for observable socio-economic characteristics. Moreover, English auction bids also exhibit significantly less residual variance and may be sensitive to the number of rival bidders. It appears that the real-time learning allowed in the English auction significantly affects subject behavior. We also find that values elicited with the Becker, DeGroot and Marshak institution differ from those in both English and Vickrey auctions. Received November 1993/Final version May 1995     

Robust strategic bidding in auction-based markets

In this paper, we propose an alternative methodology for devising revenue-maximizing strategic bids under uncertainty in the competitors’ bidding strategy. We focus on markets endowed with a sealed-bid uniform-price auction with multiple divisible products. On recognizing that the bids of competitors may deviate from equilibrium and are of difficult statistical characterization, we proposed a two-stage robust optimization model with equilibrium constraints aiming to devise risk-averse strategic bids. The proposed model is a trilevel optimization problem that can be recast as a particular instance of a bilevel program with equilibrium constraints. Reformulation procedures are proposed to find a single-level equivalent formulation suitable for column-and-constraint generation (CCG) algorithm. Results show that even for the case in which an imprecision of 1% is observed on the rivals’ bids in the equilibrium point, the robust solution provides a significant risk reduction (of 79.9%) in out-of-sample tests. They also indicate that the best strategy against high levels of uncertainty on competitors’ bid approaches to a price-taker offer, i.e., bid maximum capacity at marginal cost.     

预算约束下广义第二价格关键字拍卖均衡分析

在关键字拍卖中,广告主预算约束是影响投标策略均衡的重要因素。针对广泛应用的广义第二价格机制,分析了预算约束下的关键字拍卖均衡性质。按照广告主的点击估价和预算分布情况,将广告主划分为天然完全赢家、天然部分赢家和天然输家这三种类型,提出了广告主投标临界值与关键值的概念,基于关键字拍卖不断重复进行的特点,分别从长期视角与短期视角建立了静态模型与动态模型,研究结果表明:静态环境下拍卖存在唯一的纯策略纳什均衡;动态环境下当广告主采用最优反应投标策略时拍卖将收敛至唯一的纳什均衡点,并且动态环境下拍卖商收入不低于静态环境下的拍卖收入。数值算例的结果表明在动态环境下不同的初始报价会导致拍卖收敛至不同的均衡点。研究结果为拍卖商提供了拍卖收入预测和拍卖机制优化的决策依据。     

Coordination in a two-stage capacitated supply chain with multiple suppliers

The aim of this paper is to coordinate the inventory policies in a decentralized supply chain with stochastic demand by means of contracts. The system considered is a decentralized two-stage supply chain consisting of multiple independent suppliers and a manufacturer with limited production capacities. The suppliers operate on a make-to-stock basis and apply base stock policy to manage their inventories. On the other hand, the manufacturer employs a make-to-order strategy. Under the necessary assumptions, each supplier is modeled as an M/M/1 make-to-stock queue; and the manufacturer is modeled as a GI/M/1 queue after deriving an approximate distribution for the interarrival times of the manufacturer. Once the supply chain is modeled as a queuing system, centralized and decentralized models are developed. Comparison of the optimal solutions to these models reveals that the supply chain needs coordination. Three different transfer payment contracts are examined in this paper. These are the backorder and holding cost subsidy contracts, the transfer payment contract based on Pareto improvement, and the cost sharing contract. Each contract is evaluated according to its coordination ability and whether it is Pareto improving or not. The results indicate that all three contracts can coordinate the supply chain. However, when the Pareto improvement is taken into account, the cost sharing contract seems to be the one that will be preferred by all parties.     

A note on expected rent in auction theory

The expected rent in a reverse (buyer's) auction is shown to be monotonically nonincreasing in the number of bidders if the distribution of valuations is DRHR (IFR). Conditions under which an increase in the spread of bids results in an increase in the expected rent are established as well.     

面向电子逆向拍卖的多属性报价建议模型

针对多属性拍卖中报价的复杂性和现有报价指导模型的局限性,提出了一个以拍卖方的总价值提升为基本约束,以投标人的利润最大化为目标的多属性报价建议模型,并引入二元变量解决了定性属性的推荐问题。当投标人具有不同的投标能力和偏好时,模型可根据投标人的投标要求进行报价推荐;当存在单位价值相同的推荐报价时,模型设置了相应的约束以鼓励早投标行为。最后,还从理论上证明了该模型的稳定性,并通过算例说明了模型的可行性。