3.1. Setup
An organization identifies two potential projects—projects 1 and 2. The organization can either proceed with a project, , or choose no project (the outside option), .
The organization has two players: an uninformed decision maker (DM) and an informed agent (A). The agent possesses information: he/she observes a two-dimensional state of the world
defined as follows:
where
and
.
Both players are risk-neutral and aim to maximize payoffs. If the DM selects a project, both players’ payoffs depend on the state, the project, and the cost of implementation. On the contrary, if the DM chooses the outside option, each player’s payoff (or expected payoff) is zero. The payoff of player
is denoted as
:
where
,
, and
. The parameter
is drawn from a uniform distribution with support
.
The project set, the distributions of and , and the parameters are common knowledge. The parameter is publicly observed just before the DM’s decision making. The state is only observable to the agent. Before the DM chooses P, the agent sends a cheap talk message to the DM, where M is any large space (e.g., ).
Timeline:
- Step 1.
Nature selects the state . This is privately and perfectly observed by the agent.
- Step 2.
The agent sends a cheap talk message m. The DM observes this message without noise.
- Step 3.
The DM’s project cost is determined and publicly observed.
- Step 4.
The DM decides whether to implement a project or the outside option of no project .
- Step 5.
Both players’ payoffs are realized, and the game concludes.
This model incorporates two dimensions of biases—project bias and pandering bias—and a correlation between the benefits of the two projects.
The project bias pertains to the difference in preferences over projects, akin to the “preference similarity parameter” (
b) in CS [
11]. We interpret
as the level of project bias, assuming
and
as mentioned above.
Assumption implies that the DM is ex ante biased toward project 1, while implies that the DM does not always strictly prefer project 1 over project 2 under perfect information. The DM strictly prefers project 1 to project 2 given , while the DM strictly prefers project 2 over project 1 given .
On the other the hand, the agent can be ex ante biased toward either project: the agent is ex ante biased toward project 1 and project 2 if
and
, respectively. The agent is ex ante indifferent between the two projects if
. Assumption
implies that the agent does not always strictly prefer one project over the other under perfect information
4. The preference ranking of the agent under perfect information is dependent on the parameter. If
, the agent strictly prefers project 1 over project 2 given
, while the agent strictly prefers project 2 over project 1 given
. If
, the agent strictly prefers project 1 over project 2 given
, while the agent strictly prefers project 2 over project 1 given
.
The pandering bias is related to the preference for the outside option of no project, represented by , the cost incurred by player j when a project is implemented. For simplicity, , and follows a uniform distribution with support . The agent never finds the outside option optimal, while the DM may prefer the outside option in certain states.
The parameter
is
the correlation coefficient between
and
. Additionally, for both players,
is the correlation coefficient between the benefits of the two projects
5.
While our setup is different in some aspects, it is essential to note that
similar to CDK’s model with multiple projects and continuous states, and
is similar to Chiba and Leong’s (2015) [
4] model with two states and two projects (see
Figure 1). The value of
depends on the pair of projects being compared in a uniform quadratic example of CS, where there are continuous projects and continuous states.
We choose not to adopt a setup directly comparable to existing literature like CDK [
2] and CS [
1]. Here are the reasons for our departure:
First, we consider four states for two projects, deviating from CDK, CS, and Chiba and Leong (2015) [
4], who assumed continuous states and either discrete or continuous projects. This choice helps explain the impact of the correlation between the benefits of the two projects on information transmission. Additionally, our setup isolates the parameter
, influencing the correlation of the two projects’ benefits for both players without affecting the mean or variance of a project for any player.
Next, in CDK’s model of pandering, project costs are predetermined and publicly known
6.
However, we introduce an analysis of the interaction between pandering bias and project bias. The assumption of continuous project costs is more general from a theoretical standpoint, although our main result remains unchanged even with the fixed cost assumption.
3.2. Results
The solution concept employed is Perfect Bayesian Equilibrium (PBE). The agent’s strategy is represented by a function
, linking each state
with a message distribution used by the agent in that state. The DM’s strategy is denoted as
, associating the agent’s message
m and the DM’s cost
with the DM’s decision
P. The DM’s belief is captured by a function
, where
and
reflecting the DM’s posterior as a function of
m by Bayes’ rule.
The interaction between project and pandering biases can either reinforce or counteract each other, impacting information transmission and welfare. Crucially, we demonstrate that this counteracting effect hinges on the correlation in project benefits. As the correlation coefficient approaches , the project bias exerts a stronger influence, opposing the direction of the pandering bias. Consequently, a larger project bias can enhance information transmission and improve welfare.
Our initial lemma, akin to CDK’s Lemma 1 (CDK [
2], p. 57), states that the agent consistently favors a project over the outside option. The agent tactically selects messages to maximize the probability of his/her preferred project being chosen, either by revealing his/her preference or withholding information entirely. Consequently, the agent needs at most two messages.
Lemma 1. Every PBE is equivalent to one where the agent’s strategy involves at most two messages.
To streamline our analysis, we adopt a binary message set
. Without loss of generality, we focus on equilibria where the agent’s strategy complies with:
This implies that the agent more frequently recommends project 1 in scenarios where it is superior for both players than in the reverse situation.
The subsequent lemma adapts CDK’s Lemma 2 from their discrete project and continuous state model (CDK [
2], pp. 57–58) to our discrete state and discrete project framework.
Lemma 2. For any PBE, the following statements hold:
- (1)
If holds, then,holds. - (2)
If or holds, thenhold. - (3)
If holds, thenholds.
Lemma 2 establishes that, if the agent sends with a positive probability given , then the agent sends for sure given any . Similarly, if the agent sends with a positive probability given , then the agent sends for sure given any . If the agent mixes between two messages given at least either of and , then, he/she sends for sure given and for sure given , respectively.
We will define the types of equilibria based on CDK’s terminology:
Definition 1. (1) In a truthful equilibrium (T), for any and and for any m.
- (2)
In a pandering-toward-1 equilibrium (P1), for any and and for any m.
- (3)
In a pandering-toward-2 equilibrium (P2), , for some and and for any m.
- (4)
In a pandering-toward-2 equilibrium’ (P2’), and for any and for any m.
- (5)
In a zero equilibrium (Z), for any and for any m.
In a zero equilibrium (Z), the agent does not reveal any information. The remaining equilibria are partition equilibria, where the agent partitions the state space into two parts and discloses which partition the state
belongs to (see
Figure 2).
The first four equilibria, namely T, P1, P2, and P2’, are referred to as informative equilibria. Equilibrium messages are interpreted in two ways: indicating a ranking between the two projects or recommending a specific project. In an informative equilibrium, the agent can induce either project by sending () with a positive probability. In a zero equilibrium, there is no information transmission, and the agent can only induce project 1 or the outside option, regardless of the message sent.
According to the first interpretation, in T, the agent consistently discloses the true ranking for the decision maker (DM). As explained in the previous section, under perfect information, the DM strictly prefers project 1 over project 2 given , while the DM strictly prefers project 2 over project 1 given . Hence, in T, given any state, the agent truthfully recommends a project that the DM should prefer. Therefore, we call this a truthful equilibrium. This equilibrium is not a full revelation equilibrium. As we will show, a full revelation equilibrium does not exist in this model.
In P1, the agent recommends project 1, which is ex ante preferred by the DM, more often than in T. Hence, we call this a pandering-toward-1 equilibrium. In P2 and P2’, the agent recommends project 2 more often than in T. Hence, we call the two equilibria a pandering-toward-2 equilibrium and a pandering-toward-2 equilibrium’, respectively.
In the second interpretation, the agent uses her/his information on the state and recommends either project in an informative equilibrium, whereas the agent always recommends project 1 regardless of her/his information in a zero equilibrium.
Based on Blackwell’s informativeness, the agent transmits more information to the DM in any of T, P1, P2, and P2’ than in Z because the information transmitted in Z is constructed by garbling of the information transmitted in any of T, P1, P2, and P2’. However, we cannot compare the informativeness among T, P1, P2, and P2’ in Blackwell’s sense.
The subsequent lemma presents a characterization of all equilibria for fixed parameters and compares their welfare.
Lemma 3. For any fixed parameters, the following statements hold:
- (1)
There exist at most two types of equilibria, an informative equilibrium (T, P1, P2, or P2’) and a zero equilibrium (Z). Moreover, Z always exists.
- (2)
There is a unique informative equilibrium if T, P1, or P2’ exists.
- (3)
If an informative equilibrium exists, the informative equilibrium makes both players better off than Z.
Lemma 3 shows that multiple types of informative equilibria do not exist together. Only possible multiplicity is one type of informative equilibrium (T, P1, P2, or P2’) and a zero equilibrium (Z). When T, P1, or P2’ exists, this is the unique informative equilibrium. However, when P2 exists, there can be multiple P2s. Moreover, the informative equilibrium is better than a zero equilibrium for both players.
Because of Lemma 3, if there is T, P1, or P2’, we focus on the unique informative equilibrium. If there is P2, meaning that multiple P2s can exist, we will focus on the one that maximizes the DM’s ex ante expected payoff. Otherwise, we consider Z. Accordingly, the following result provides comparative statics across parameters
7.
Proposition 1. Then, for any fixed , ρ, and l:
- (1)
A truthful equilibrium (T) exists for ;
- (2)
A pandering-toward-1 equilibrium (P1) exists for ;
- (3)
A pandering-toward-2 equilibrium (P2) exists for - (4)
A pandering-toward-2 equilibrium’ (P2’) exists for if ;
- (5)
The only equilibrium is a zero equilibrium (Z) otherwise.
Furthermore, the DM’s ex ante expected payoff is not monotonic in if .
Figure 3 illustrates the most informative type of equilibrium for various values of
and
, given
and
. According to the definitions, the following holds:
For , line distinguishes areas for P2 and Z, respectively. When , line separates areas for P2 and P2’. Notably, for smaller , informative equilibria (T, P1, P2, or P2’) exist in a narrower range of . Furthermore, if is so small that , the truthful equilibrium (T) exists only for .
Later, we will come back to
Figure 3 and explain how we define lines separating the space of parameters
into the parts where an informative equilibrium (T, P1, P2, or P2’) exists and the part where only Z exists.
Figure 4 and
Figure 5 show the ex ante expected payoff of the DM and the agent, respectively, for different levels of
, given
,
, and
, that is
. For both players’ payoffs, there is a jump at
, below which a pandering-toward-2 equilibrium (P2) exists, and above which only a zero equilibrium (Z) exists.
To explain the intuition behind this result, we outline the proof. Let
represent the DM’s updated belief about
when the agent sends message
, where
i,
j are in the set
. In an informative equilibrium, the DM should agree with the project ranking (or recommendation) proposed by the agent. The following two conditions must be satisfied.
and
Condition (8) implies that, when the agent sends (suggesting that project 1 is better than project 2), the DM also favors project 1 over project 2. Condition (9) means that, when the agent sends , the DM prefers project 2 over project 1. Due to the DM’s inherent bias toward project 1, (8) holds in every type of equilibrium, while (9) may not. If both (8) and (9) hold, the DM implements a recommended project if the cost is below the expected benefit from the project. Specifically, the DM selects if and ; if and ; and otherwise.
Conversely, in an informative equilibrium, the agent should also have the incentive to disclose information. Hence, for a truthful equilibrium (T) to exist, in addition to (8) and (9), the following two conditions should also hold:
Condition (10) holds given
in T. In addition:
Confition (11) holds given
in T. Condition (10) indicates that the agent aims to induce project 1 (i.e., sends
). Condition (11) implies the agent’s aims to induce project 2 (i.e., sends
). For example, in a truthful equilibrium (T), the DM’s consistent beliefs are:
To verify the existence of this equilibrium, we check whether conditions (8)–(11) hold based on these beliefs. Similar checks are performed for other types of equilibria, and it can be easily shown that multiple types of informative equilibrium do not exist.
According to conditions (8)–(11), a smaller (stronger DM bias toward project 1) results in a more pronounced pandering bias. The agent is more inclined to recommend project 1 as suggesting project 2 leads to a reduced probability of implementation. Moreover, for smaller , the DM finds a ranking where project 2 is superior to project 1 less agreeable.
Figure 3 can be explained as follows, associated with conditions (8)–(11). The space of parameters
is separated into multiple parts with regard to which type of informative equilibrium exists. We call the part where T exists
the area for T.
The areas for P1, P2, and P2’ are defined similarly. We call the part where only Z exists
the area for Z.
Start with a point in the area for T, where (the DM’s ex ante bias toward project 1 is strong). Then, we increase with held fixed. As increases, the agent becomes more biased toward project 2, and hence, the agent is willing to recommend project 2 (i.e., condition (10) is violated) given in T. As a result, the informative equilibrium existing changes from T to P2. This transition defines the borderline between the areas for T and P2.
As increases further, the agent is biased toward project 2 further. The agent recommends project 2 more frequently, which reduces the DM’s belief on the benefit from project 2 and allows condition (10) to be satisfied given in P2. But, once the DM’s belief about the benefit from project 2 goes under some cutoff level, the DM ignores the agent’s recommendation of project 2 and chooses project 1. As a result, the informative equilibrium existing changes from P2 to none (i.e., only Z exists). This transition defines the borderline between the areas for P2 and Z.
Again, start with a point in the area for T where (the DM’s bias is strong). Now, we decrease with held fixed. As decreases, the agent becomes more biased toward project 1, and hence, the agent is willing to recommend project 1 (i.e., condition (11) is violated) given in T. As a result, the informative equilibrium existing changes from T to P1. This transition defines the borderline between the areas for T and P1.
As
decreases further, the agent is biased toward project 1 further. The agent recommends project 1 more frequently, which reduces the DM’s belief about the benefit from project 1 and allows condition (11) to be satisfied with equality given
in P1. But, eventually, the agent always recommends project 1 given any state, and condition (11) is violated given
in P1. As a result, the informative equilibrium existing changes from P1 to none (i.e., only Z exists). This transition defines the borderline between the areas for P1 and Z
8.
When the DM’s ex ante bias is so weak that
, the area for P2’ exists, while each borderline is defined similarly. Even if
continues to increase and the agent recommends project 2 more frequently in P2 than in T, the DM still obeys the agent’s recommendation of project 2 (i.e., condition (9) is satisfied). As
increases further, the agent does not recommend project 1 at all (i.e., condition (10) is violated) given
in P2. As a result, the informative equilibrium existing changes from P2 to P2’. This transition defines the borderline between the areas for P2 and P2’
9.
Next, we discuss the welfare implications. Let
represent the DM’s ex ante expected payoffs in a truthful equilibrium (T). Similar notations are used for the ex ante expected payoff in other equilibrium types, denoted as
and
. The specific expressions are found in
Appendix A. For any type of equilibrium X in {T, P1, P2, P2’, Z}, the DM’s ex ante expected payoff is given by:
For any fixed parameters, the DM fares better in the informative equilibrium compared to the zero equilibrium.
To compare payoffs across parameters, the following observations are important.
Fix and l, then:
- (1)
T, P1, P2, and Z exist for small , while only T, P2, and P2’ exist (i.e., P1 does not exist) for large .
- (2)
For any
,
regardless of
.
- (3)
strictly increases with .
- (4)
- (5)
For any
,
regardless of
.
- (6)
strictly decreases with .
- (7)
These observations lead to the conclusion that, for , the truthful equilibrium (T) exists only when . Consequently, the DM’s ex ante expected payoff is not monotonic in . Additionally, given and l, varying levels of significantly impact the DM’s payoff for small , while the effect diminishes for large . Therefore, it is reasonable to focus on the non-monotonicity given .
A similar argument extends to the agent’s ex ante expected payoff.
Corollary 1. For any fixed , ρ, and l, the agent’s ex ante expected payoff is not monotonic in if .
Let
denote the agent’s ex ante expected payoffs in a type X equilibrium for
. Since the agent does not bear the cost of implementing a project, his/her expected payoff is given by:
We omit remaining details for the agent’s ex ante expected payoffs. Finally, we present our main claim that the non-monotonicity between information transmission and the project bias is significant when the correlation is closer to .
Proposition 2. Fix l. Then, strictly decreases with ρ. Furthermore, fix l and . Then:
- (1)
strictly decreases with ρ.
- (2)
for any ρ.
- (3)
strictly decreases with ρ.
- (4)
only for small ρ.
Proposition 2 directly follows from expressions (12) and (13), as well as the DM’s inferences in each type of equilibrium. As mentioned earlier, when
, information transmission does not exhibit monotonicity in
. The first part of Proposition 2 indicates that the non-monotonicity becomes more prevalent with a highly negative correlation.
Figure 6 compares the most informative equilibrium and the cutoff
for
and various
.
The second part of Proposition 2 suggests that the non-monotonicity in information transmission has a more pronounced impact, at least on the DM’s ex ante expected payoff.
Figure 7 and
Figure 8 compare the ex ante expected payoffs of the DM and the agent, respectively, for
and various
.
We finish this section by discussing the applicability of our results to the model with continuous states. Lemmas 1–3 and Proposition 2 hold in a similar manner in such models. That is, if there is an informative equilibrium, the agent divides the entire state space (a subspace of the two-dimensional euclidean space) by the straight line going through the origin and, then, reveals which part the true state belongs to (i.e., the agent recommends one project over the other). Given fixed
, the dividing line rotates clockwise around the origin (i.e., the agent recommends project 2 more frequently) as
increases (i.e., the agent becomes more biased toward project 2). However, we do not know how to define correlations among continuous states and compare the outcome across different levels of correlations. Hence, this paper focuses on the simple state space (with four points), which results in partition equilibria (as shown in CDK [
2]) and allows the examination of different levels of correlations (which is not performed in CDK).