摩擦市场中的筛选与逆向选择：经济学研究

版权申诉

72 浏览量更新于2024-07-02 收藏 1.34MB PDF 举报

"本文探讨了筛选和逆向选择在摩擦性市场中的作用，由联邦储备银行的Benjamin Lester、卡内基梅隆大学的Ali Shourideh、纽约大学斯特恩商学院的Venky Venkateswaran和卡内基梅隆大学的Ariel Zetlin-Jones合作撰写。" 在经济学领域，筛选和逆向选择是两个关键概念，特别是在理解不完全信息和非均衡市场行为时。这篇研究论文聚焦于这些概念如何在存在摩擦的市场中影响交易过程和市场效率。筛选（Screening）是指在市场中，卖方或买方通过设定价格或其他条件来获取关于对方的信息，以便确定最佳交易伙伴的过程。在摩擦性市场中，由于信息不对称，卖方可能无法准确了解所有潜在买家的真实需求或能力，反之亦然。因此，筛选机制成为一种解决信息不对称问题的策略，例如，雇主通过设置面试或测试来评估应聘者的技能，或者银行通过信用评分系统筛选借款人。逆向选择（Adverse Selection）则发生在信息不对称导致的市场失衡情况下，即高质量的商品或服务被低质量的所取代。当买方无法区分商品的优劣时，他们可能会根据平均价格进行购买，这可能导致优质商品的供应商退出市场，因为他们的产品无法获得相应的高价。经典的例子是二手车市场，其中卖家通常比买家更了解车辆的实际状况，导致买家倾向于假设所有二手车都有质量问题，从而压低价格。文章可能深入分析了在不同类型的摩擦性市场（如劳动力市场、金融市场和商品市场）中，筛选和逆向选择如何影响市场效率、资源配置和稳定性。作者们可能通过理论模型和实证分析来展示这些概念在实际经济活动中的运作方式，并可能提出政策建议，以减少信息不对称带来的负面影响，促进市场的健康发展。论文的广泛讨论和审阅，包括在多个经济学研讨会和会议上，表明了这个主题的重要性和研究的严谨性。参与者和评论者来自各种经济学领域的专家，如Gadi Barlevy、Hanming Fang、Mike Golosov等，这反映了学术界对筛选和逆向选择问题的广泛关注。这篇论文对于理解摩擦性市场中的经济行为、市场设计和政策制定具有重要意义，它提供了对筛选和逆向选择现象的深入洞察，并可能为解决这些复杂问题提供新的思路。

Note that this deﬁnition imposes two requirements. The ﬁrst is that buyers behave

optimally: for each u

, the joint probability measure puts a positive weight only on

∈ U

(

)

. The second is aggregate consistency, i.e., that F

and F

are marginal

distributions associated with a joint measure of menus.

3.3 Basic Properties of Equilibrium Distributions

In this section, we establish that, in equilibrium, the distributions F

) and F

) are

continuous and have connected support, i.e., there are neither mass points nor gaps in

either distribution.

Proposition 1. The marginal distributions F

and F

have connected support. They are also

continuous, with the possible exception of a mass point in F

at v

As in Burdett and Judd (1983), the proof of Proposition 1 rules out gaps and mass

points in the distribution by constructing proﬁtable deviations. A complication that

arises in our model, which does not arise in Burdett and Judd (1983), is that payoffs

are interdependent, e.g., a change in the utility offered to low-quality sellers changes

the contract—and hence the proﬁts—that a buyer receives from high-quality sellers. We

prove the properties of F

and F

described in Proposition 1 sequentially: we ﬁrst show

that F

is continuous and strictly increasing, and then apply an inductive argument to

prove that F

has connected support and is continuous, with a possible exception at

the lower bound of the support. An important step in the induction argument, which

we later use more generally, is to show that the objective function Π

(

, u

)

is strictly

supermodular. We state this here as a lemma.

Lemma 2. The proﬁt function is strictly supermodular, i.e.,

(

, u

)

+ Π

(

, u

)

> Π

(

, u

)

+ Π

(

, u

)

, ∀u

> u

, i ∈

{

l, h

}

with strict inequality when u

> u

, i ∈

{

l, h

}

Please use DOI when citing or quoting. DOI: 10.1086/700729

This content downloaded from 185.216.093.030 on September 29, 2018 14:07:37 PM

All use subject to University of Chicago Press Terms and Conditions (http://www.journals.uchicago.edu/t-and-c).

As noted above, the supermodularity of the buyer’s proﬁt function reﬂects a basic

complementarity between the indirect utilities offered to low- and high-quality sellers.

An important implication is that the correspondence U

(

)

is weakly increasing. We

use this property to construct deviations to rule out gaps and mass points in the distri-

bution F

almost everywhere in its support; later, in Section 4, we show that these mass

points only occur in a knife-edge case. Hence, generically, the marginal distribution F

has connected support and no mass points in its support.

3.4 Strict rank-preserving

In this section, we establish that every equilibrium has the property that the menus being

offered are strictly rank-preserving—that is, low- and high-quality sellers share the same

ranking over the set of menus offered in equilibrium—with the possible exception of

the knife-edge case discussed above. We prove this result by showing that the mapping

between a buyer’s optimal offer to low- and high-quality sellers, U

), is a well deﬁned,

strictly increasing function. We start with the following deﬁnition.

Deﬁnition 1. For any subset U

of Supp

(

)

, an equilibrium is strictly rank-preserving over

if the correspondence U

(

)

is a strictly increasing function of u

for all u

∈ U

. An

equilibrium is strictly rank-preserving if it is strictly rank-preserving over Supp

(

)

Equivalently, an equilibrium is strictly rank-preserving if, for any

(

, u

)

and



, u



in the equilibrium support, u

> u

if and only if u

> u

. Given this terminology, we

now establish a key result.

Theorem 1. All equilibria are strictly rank-preserving over the set Supp

(

)

{

}

Theorem 1 follows from the facts established above. In particular, the strict super-

modularity of Π(u

, u

) implies that U

(

)

is a weakly increasing correspondence.

However, since F

(

)

and F

(

)

are strictly increasing and continuous, we show that

) can neither be multi-valued nor have ﬂats. Intuitively, if there exists a u

min Supp(F

) ≡ u

and u

> u

such that u

, u

∈ U

), then the supermodularity of

Π(u

, u

) implies that [u

, u

] ⊂ U

). Since F

(·) has connected support, if U

were

Please use DOI when citing or quoting. DOI: 10.1086/700729

This content downloaded from 185.216.093.030 on September 29, 2018 14:07:37 PM

All use subject to University of Chicago Press Terms and Conditions (http://www.journals.uchicago.edu/t-and-c).

a correspondence for some u

, then this would imply that F

(·) must have a mass point

at u

, which contradicts Proposition 1. Similarly, if there exists u

and u

> u

offered

in equilibrium such that U

) = U

) = u

, then F

would feature a mass point, in

contradiction with Proposition 1. Hence, U

) must be a strictly increasing function for

all u

> u

If F

(·) is continuous everywhere, then every menu offered in equilibrium is accepted

by the same fraction of low- and high-quality noncaptive sellers; we state this formally

in the following Corollary.

Corollary 2. If F

and F

are continuous, then F

)) = F

Taken together, Theorem 1 and Corollary 2 simplify the construction of an equilib-

rium. Speciﬁcally, when an equilibrium exists in which the marginal distributions are

continuous, then the equilibrium can be described compactly by the marginal distribu-

tion F

) and the function U

4 Construction of Equilibrium

In this section, we use the properties established above to construct equilibria. Then,

we show that the equilibrium we construct is unique. In this sense, we characterize the

entire set of equilibrium outcomes.

4.1 Special Cases: Monopsony and Perfect Competition

To ﬁx ideas, we ﬁrst characterize equilibria in the well-known special cases of π = 0 and

π = 1, i.e., when sellers face a monopsonist and when they face two buyers in Bertrand

competition, respectively. As we will see, several features of the equilibrium in these two

extreme cases guide our construction of equilibria for the general case of π ∈ (0, 1).

When π = 0, so that each seller meets with at most one buyer, the buyers solve

max

)

− u

) + µ



− u

− c

+ u

− c



Please use DOI when citing or quoting. DOI: 10.1086/700729

This content downloaded from 185.216.093.030 on September 29, 2018 14:07:37 PM

All use subject to University of Chicago Press Terms and Conditions (http://www.journals.uchicago.edu/t-and-c).

subject to the monotonicity and feasibility constraints in (7). The solution to this prob-

lem, summarized in Lemma 3 below, is standard and, hence, we omit the proof.

Lemma 3. Suppose π = 0, and let

≡ 1 −



− c



. (13)

If φ

> 0, then the unique equilibrium has u

= c

with x

= 1 and u

= c

with x

= 0; if

< 0, then u

= u

= c

with x

= x

= 1; and if φ

= 0, then u

∈ [c

, c

] with x

= 1 and

= c

with x

∈ [0, 1].

The parameter φ

is a summary statistic for the adverse selection problem: it repre-

sents the net marginal cost (to the buyer) of delivering an additional unit of utility to a

low-quality seller. It is strictly less than 1 because the direct cost of an additional unit of

transfer to a low-quality seller is partially offset by the indirect beneﬁt of relaxing this

seller’s incentive constraint, which allows the buyer to trade more with a high-quality

seller. This indirect beneﬁt is captured by the second term on the right-hand side: when

this term is large, φ

is small, the cost of trading with high-quality sellers is low, and

adverse selection is mild. Conversely, when this term is small, φ

is large, it is costly to

trade with high-quality sellers, and therefore adverse selection is relatively severe. Ac-

cording to this measure, adverse selection is thus severe when the relative fraction of

high-quality sellers, µ

/µ

, is small; the gains from trading with high-quality sellers,

− c

, are relatively small; and/or the information rents associated with separating

high- and low-quality sellers, c

− c

, are large.

When φ

> 0, the net cost to a buyer of increasing u

is positive, so she sets u

low as possible, i.e., u

= c

. This implies that the high-quality seller is entirely shut out,

i.e., x

= 0. Otherwise, when φ

< 0, increasing u

yields a net beneﬁt to the buyer. As

a result, a buyer raises u

until the monotonicity constraint in (7) binds, i.e., she pools

high- and low-quality sellers, offering u

= u

= c

Before proceeding to the perfectly competitive case, we highlight two features of the

equilibrium under monopsony. First, buyers offer separating menus (u

> u

) when φ

Please use DOI when citing or quoting. DOI: 10.1086/700729

This content downloaded from 185.216.093.030 on September 29, 2018 14:07:37 PM

All use subject to University of Chicago Press Terms and Conditions (http://www.journals.uchicago.edu/t-and-c).

is positive and pooling menus (u

= u

) when φ

is negative. Second, they make non-

negative payoffs on both types when φ

> 0, but lose money on low-quality sellers when

< 0. In other words, the equilibrium features cross-subsidization when φ

is negative,

but not when φ

is positive.

When competition is perfect, i.e., when π = 1, our setup becomes the same as that in

Rosenthal and Weiss (1984), and similar to that of Rothschild and Stiglitz (1976). In this

case, when φ

> 0, the unique equilibrium is in pure strategies, with buyers offering the

standard “least-cost separating” contract; type l sellers earn u

= v

and type h sellers

trade a fraction of their endowment at a unit price of v

, such that the incentive con-

straint of the low-quality seller binds. However, when φ

< 0, there is no pure strategy

equilibrium.

In this case, an equilibrium in mixed strategies emerges, as in Rosenthal

and Weiss (1984) and Dasgupta and Maskin (1986).

Each buyer mixes over menus,

all of which involve negative proﬁts from low-quality sellers, offset exactly by positive

proﬁts from high-quality sellers, leading to zero proﬁts. The marginal distribution F

(·)

is such that proﬁtable deviations are ruled out. The following lemma summarizes these

results.

Lemma 4. When π = 1, the unique equilibrium is: (i) if φ

> 0, then u

= v

, x

= 1,

(

−c

)

(

−c

)

−c

, and x

−c

; (ii) if φ

< 0, then the symmetric equilibrium is

described by the distribution

(

)



− v

(

− v

)



−φ

, (14)

with Supp

(

)

[

, ¯v

]

and F

) = F

)), where ¯v = µ

+ µ

and U

(

)

satisﬁes

(

, U

(

))

+ µ

(

, U

(

))

= 0. (15)

All buyers offering the least-cost separating contract cannot be an equilibrium, as a pooling offer is

proﬁtable. All buyers offering a pooling contract cannot be an equilibrium either, since it is vulnerable to

a cream-skimming deviation, wherein a competing buyer draws away high-quality sellers by offering a

contract with x < 1 but at a higher price.

Luz (2017) shows that the equilibrium is unique.

Please use DOI when citing or quoting. DOI: 10.1086/700729

This content downloaded from 185.216.093.030 on September 29, 2018 14:07:37 PM

All use subject to University of Chicago Press Terms and Conditions (http://www.journals.uchicago.edu/t-and-c).

剩余104页未读，继续阅读

samLi0620

粉丝: 1190
资源: 1万+

摩擦市场中的筛选与逆向选择：经济学研究

Simulation of Screening Process Based on MATLAB_Simulink.pdf

Sure Independence Screening and Sparsifying Operator 特征生成代码

Sure Independence Screening and Sparsifying Operator) 完整代码，生成的特征要包含加减乘除的运算

妊娠期糖尿病相关中英文杂志

atom pair fingerprint

化合物评价函数2020年之后的文献

如何使用Python自动运行MySQL数据库进行比中弹屏

room1.setScreening_time(scanner2.nextLine());

有提及细胞增殖速度可能影响CCK8检测结果20篇参考文献

最新资源