I've done a few client specific network / marketplace financial modeling as well as a few templates for this industry. There are a lot of ways to create a financial forecast for a place that facilitates commerce between two or more parties. Note, some things just can't be simulated that well in Excel or Google Sheets, but some can.

There are various marketplace modeling approaches that can be used to analyze and understand the dynamics of a marketplace. Here are some general marketplace modeling approaches:

**Supply-Demand Modeling**: This approach focuses on the interactions between the supply and demand sides of the marketplace. It uses models such as linear regression, time series analysis, and econometric models to forecast the demand and supply patterns in the market. A similar template I've done for this involved a network model focused publisher and advertiser activity.

**Network Effects Modeling**: One of the main reasons why I incorporate many assumption inputs that can be changed over time are to account for this dynamic. This approach examines the effects of network externalities on the marketplace. Network effects occur when the value of a product or service increases as more people use it. Models such as the Bass diffusion model and the S-shaped adoption curve model can be used to analyze network effects in the market.

- Bass Diffusion Model - The Bass diffusion model is a mathematical model that describes the adoption of new products or technologies in a market. It was introduced by Frank Bass in 1969 and has become a widely used model in marketing and innovation research.

- The Bass diffusion model assumes that the rate of adoption of a new product or technology is influenced by two factors: the innovators who are likely to adopt the product early on, and the imitators who are influenced by the actions of the innovators. The model is based on the following two equations:

- dN(t)/dt = p(1-N(t)/m) + qN(t)^(m-1)

- where N(t) is the cumulative number of adopters at time t, p is the coefficient of innovation, q is the coefficient of imitation, and m is the market potential (the maximum number of potential adopters). Generally, in most of the financial models I built, there are areas to manually input what the result of this formula would be, but because you never know how a given business may want to forecast their demand, I generally make the slots with arbitrary input cells that can be modified.

- The first term in the equation represents the effect of innovation, and the second term represents the effect of imitation. The model assumes that the rate of adoption of a new product is highest at the beginning when the number of adopters is small and decreases over time as the market becomes saturated.

- An example of the Bass diffusion model in action is the adoption of smartphones. Initially, a small number of innovators purchased smartphones when they were first introduced. As more people saw these innovators using smartphones and realized their benefits, the rate of adoption increased among imitators. Over time, as more people adopted smartphones, the rate of adoption slowed down until it reached its maximum market potential.

- Another example is the adoption of electric cars. As electric cars become more affordable and more widely available, the rate of adoption is likely to increase, starting with early adopters who are interested in new technology and sustainable transportation. Over time, as more people see these early adopters using electric cars, the rate of adoption is likely to increase among imitators until it reaches its maximum market potential.

- The Bass diffusion model is useful for businesses to forecast the potential demand for new products and to develop effective marketing strategies to reach different segments of potential adopters.

**Game Theory Modeling**: Game theory models the strategic interactions between different players in the marketplace. It provides a framework for understanding how players interact, what motivates their behavior, and how they respond to different market conditions. Models such as the prisoner's dilemma and the Nash equilibrium are commonly used in game theory.

**Prisoner's Dilemma**- The Prisoner's Dilemma is a classic model in game theory that describes a situation in which two individuals, acting in their own self-interest, do not achieve the optimal outcome. It is a scenario where two suspects are arrested and held in separate cells, and they are given a choice to either cooperate with each other and remain silent or to betray the other and confess to the crime.

- If both suspects remain silent, they will both be sentenced to a short prison term for a minor crime. If both confess, they will both receive a longer sentence for a more serious crime. If one remains silent and the other confesses, the one who confesses will be given a reduced sentence, and the one who remains silent will receive a longer sentence.

- The dilemma arises from the fact that each prisoner must choose whether to betray the other or cooperate with them without knowing what the other will do. If both prisoners cooperate, they will both receive the best outcome. However, if one betrays the other, they will receive a better outcome, while the other receives the worst outcome. If both betray each other, they will both receive a worse outcome.

- The Prisoner's Dilemma is used to illustrate the conflict between individual rationality and the collective interest. In many situations, cooperation can lead to a better outcome for everyone, but individual self-interest may lead people to choose betrayal instead. The Prisoner's Dilemma is a useful model for understanding a range of real-world situations, including business competition, international relations, and social dilemmas.

**Economic Modeling**: Economic modeling uses economic theory to analyze market dynamics. It considers factors such as market structure, pricing strategies, and competition. Models such as the Cournot model, the Bertrand model, and the Stackelberg model can be used to analyze different market structures and pricing strategies. See more on these modeling strategies below.

**Simulation Modeling**: Simulation modeling involves creating a computer model of the marketplace and simulating different scenarios to see how the market behaves. This approach can be used to test different strategies, evaluate the impact of policy changes, and explore potential outcomes under different conditions.

**Building Your Own Financial Model**

**Define the key variables and parameters**: To build an effective model, it's important to clearly define the key variables and parameters that will impact the network or marketplace business. These may include factors such as customer acquisition costs, network effects, transaction fees, and user behavior.

**Incorporate network effects**: Network effects are a critical factor in modeling a network or marketplace business. Consider how the growth of the network impacts user behavior, market dynamics, and revenue streams.

**Account for user behavior:**The behavior of users on the network or marketplace can be difficult to predict, but it's important to consider how different user groups may interact with the platform. This can include factors such as user preferences, decision-making processes, and response to incentives.

**Validate the model**: To ensure that the model is accurate and effective, it's important to validate it against real-world data. This may involve testing the model against historical data, conducting simulations, or comparing the model to data from other similar networks or marketplaces.

**Involve Stakeholders**: Anyone who as an interest your your business succeeding may also have insights and want to review your model to see if anything is being overlooked or needs closer attention.

Overall, each of these marketplace modeling approaches can be used to provide valuable insights into the dynamics of a marketplace and help businesses make informed decisions.

**More on Prisoner's Dilemma and Nash equilibrium in Financial Modeling**

The Prisoner's Dilemma can be used in financial modeling to analyze strategic decision-making between competitors or investors. It can be applied to situations where two or more parties have the option to either cooperate or compete with each other, and where the outcome of each decision is interdependent on the other parties' decision.

For example, in a market with two dominant firms, they can either choose to collude and set high prices or compete and set lower prices. If both firms cooperate, they can maximize their profits. However, if one firm betrays the other by lowering prices, it can increase its market share and profits, while the other firm will lose market share and profits. If both firms betray each other by lowering prices, they will both suffer lower profits.

Using the Prisoner's Dilemma in financial modeling, we can assign payoffs to each strategy depending on the outcomes. For example, we can assign a higher payoff for cooperation compared to betrayal, but a lower payoff for mutual defection. This allows us to analyze the strategic decision-making process of the firms and determine the Nash equilibrium, which is the optimal strategy for both firms.

Another example of using the Prisoner's Dilemma in financial modeling is in the analysis of investor behavior. Investors can either choose to invest in a stock or to sell it. If all investors choose to hold onto the stock, the price will increase, leading to higher profits for everyone. However, if some investors decide to sell, it can lead to a decrease in the price, causing losses for those who hold onto the stock.

Using the Prisoner's Dilemma in financial modeling can help to understand the behavior of investors and the dynamics of markets. It can also provide insights into the strategies that can maximize profits and minimize losses in different scenarios.

**Example of Nash Equilibrium Calculation**

Suppose there are two banks, Bank A and Bank B, that are considering entering a new market. They can either choose to compete aggressively or cooperate by setting moderate prices. The payoff matrix for this scenario is as follows:

In the payoff matrix, the first number represents the payoff for Bank A, and the second number represents the payoff for Bank B. For example, if both banks cooperate by setting moderate prices, they both receive a payoff of 5. If Bank A competes aggressively by setting low prices while Bank B cooperates, Bank A receives a payoff of 8, and Bank B receives a payoff of 0.

To find the Nash equilibrium, we need to identify the strategy that neither bank would want to deviate from, given the other bank's strategy. In other words, it is the outcome in which no bank has an incentive to change their strategy, assuming the other bank's strategy is fixed.

In this example, the Nash equilibrium occurs when both banks choose to compete aggressively. If Bank A competes while Bank B cooperates, Bank A gets a payoff of 8, which is higher than the payoff of 5 if both banks cooperate. Similarly, if Bank B competes while Bank A cooperates, Bank B gets a payoff of 2, which is higher than the payoff of 0 if both banks cooperate. Therefore, both banks have an incentive to compete, and this is the Nash equilibrium.

In summary, the Nash equilibrium of this financial scenario is when both banks choose to compete aggressively. By identifying the Nash equilibrium, we can better understand the strategic decision-making of the banks and the likely outcome of the scenario.

The below models fit fairly well in a manufacturing forecasting template.

**More on the Cournot Model**

The Cournot model is an economic model that describes the behavior of firms in an oligopoly market. It was developed by French economist Augustin Cournot in 1838 and is considered one of the earliest models of imperfect competition.

In the Cournot model, there are two or more firms that produce similar goods or services and compete with each other in the market. Each firm chooses its level of output based on the assumption that its competitors will keep their output levels constant. The firms simultaneously choose their output levels, taking into account the production costs and market demand.

The model assumes that each firm wants to maximize its profits and that the market demand is a function of the total output of all firms. As a result, each firm's profit depends not only on its own output but also on the output of its competitors.

The Cournot model leads to a unique equilibrium in which each firm produces a quantity of output that is less than the output that would be produced in a perfectly competitive market. This is because each firm considers the effect of its output on the market price and the output of its competitors.

The Cournot model has been used to analyze various industries, including the energy, telecommunications, and airline industries. It is also used in game theory and industrial organization to study market behavior and strategic interactions between firms.

One limitation of the Cournot model is that it assumes that firms have complete information about their competitors' costs and strategies. In reality, firms often have incomplete information and must make decisions based on imperfect information. Despite this limitation, the Cournot model remains a useful tool for understanding the behavior of firms in oligopoly markets.

**More About the Bertrand Model**

The Bertrand model is an economic model of competition in which firms produce homogeneous goods and compete on price. The model was developed by French economist Joseph Bertrand in 1883 as a response to the Cournot model of competition, which assumes that firms compete on quantity.

In the Bertrand model, firms simultaneously set prices for their products, taking into account the prices set by their competitors. The model assumes that **consumers will always purchase the product from the firm offering the lowest price**, all else being equal. As a result, firms have an incentive to set their prices as low as possible to capture the entire market.

One of the key results of the Bertrand model is that it leads to a perfectly competitive market outcome, in which firms** set prices equal to their marginal costs of production**. This outcome occurs because if a firm sets its price higher than its competitors, it will lose all its customers to the competitor with the lower price.

However, this outcome assumes that firms have no capacity constraints, no differentiated products, and no strategic interaction beyond price-setting. In reality, firms often face constraints that limit their ability to produce and sell at their marginal cost, and may engage in non-price competition through advertising, product differentiation, or other strategies.

The Bertrand model is often used as a benchmark for comparing market outcomes under different assumptions, such as imperfect competition or differentiated products. It is also used to analyze markets with zero or low marginal costs, such as digital products or services, where the marginal cost of production is negligible and price competition is fierce.

Overall, the Bertrand model provides a useful framework for understanding the dynamics of price competition in different market settings, and remains an important tool in economic theory and industrial organization.

**More on the Stackelberg Model**

The Stackelberg model is an economic model that describes the behavior of firms in an oligopoly market in which one firm acts as a leader and the other firms follow its lead. The model was developed by German economist Heinrich von Stackelberg in 1934.

In the Stackelberg model, there are two firms that produce similar goods or services and compete with each other in the market. The leader firm sets its output level first, taking into account the reaction of the follower firm. The follower firm then observes the output level of the leader and sets its own output level to maximize its profits, given the output of the leader.

The model assumes that the leader firm has an advantage in the market, such as lower production costs or better technology. As a result, the leader firm can set its output level higher than that of the follower firm, which leads to a higher market share and profits.

The Stackelberg model leads to a unique equilibrium in which the leader firm produces more output than the follower firm, but less than it would produce in a perfectly competitive market. The follower firm produces less output than the leader firm, but more than it would produce in a perfectly competitive market.

The Stackelberg model has been used to analyze various industries, including the automobile, telecommunications, and energy industries. It is also used in game theory and industrial organization to study market behavior and strategic interactions between firms.

One limitation of the Stackelberg model is that it assumes that firms have complete information about their competitors' costs and strategies. In reality, firms often have incomplete information and must make decisions based on imperfect information. Despite this limitation, the Stackelberg model remains a useful tool for understanding the behavior of firms in oligopoly markets where one firm has a dominant position.