Modern pricing in the revenue management environment
- Von Björn Piepenburg
- Classification, Cross entropy, Deep lattice network, Price sensitivity, Revenue Management
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Traditionally, offer prices for products or services are charged on the basis of the costs incurred, plus a target margin. Since the end of the last century, there has been a second approach to setting offer prices: How much is a customer willing to pay for a product or service? In the best case scenario, this price covers the costs incurred and also includes the targeted margin. The driving force behind this development was passenger transportation by air. Due to the increase in so-called low-cost airlines, the renowned airlines were forced into action and had to come up with an approach to cover their costs and still be competitive with their rivals. The idea was that, for example, business travelers who decide to travel at short notice pay more money for a ticket than city travelers with a long planning horizon. Today, this idea is spreading to different industries and products such as hotel accommodation, rental cars and freight transportation. The central question of the approach is how much a specific customer or customer group is prepared to pay for a product or service.
Reasons for acceptable prices vary greatly depending on the industry and customer. In passenger transportation or, more generally, in the tourism industry, it is certainly the lead time of the booking, flexibility, cancellation conditions, additional services such as catering and other influences. An exact individual acceptance probability depending on all influences incl. of the price cannot be calculated exactly. Even for a specific person, the weighting of the influences can change between two days. If, for example, the weather forecast deteriorates, the likelihood of last-minute city travelers buying tickets decreases. A reduction in price could neutralize the influence, but an upgrade to a different class of transport or room size could also influence the decision.
The task of a Data Scientist (m/f/d) is to estimate individual acceptance probabilities for a customer or customer group from historical transaction data, depending on all available information. The acceptance probabilities as a function of the price, taking all influences into account, are referred to as the price sensitivity curve. This generally has an S-shaped (sigmoid) course.
An example of the curve shown is a service company that places orders with tradespeople. In the case of a product price, the curve would have to be mirrored so that low prices lead to a high probability of acceptance and high prices to a low probability.
The curve can be mapped using a multidimensional (non-linear) regression model: a function is sought that maps the influencing characteristics in relation to the target variable (or also in relation to several target variables) and minimizes the deviations from the target variable actually measured. This is known as supervised learning. In our case, the target variable would be the probability of acceptance and the influencing characteristics of all information (including the price) available in the transaction data and in the customer data. There is only one problem: the target size is unknown. Although we have the information for each offer as to whether it was accepted or not, we do not know how far the offer price was from the customer’s acceptance threshold. To solve the problem, we change the target variable to the binary characteristic acceptance / rejection. This gives us a so-called logistic regression model, which we can train. What is missing now, however, are the required acceptance probabilities.
To obtain these, we change the solution method again. By using the binary target variable acceptance / rejection, we can also model the assignment of a data set to one of the two classes acceptance or rejection instead of the regression curve – a classification problem. Similar to regression, the classes are ordered in such a way that the deviations between the actual assumption behavior and the model are minimal. In mathematics, there are proven measures for the error of a model. The best known is probably the root of the mean square error over all data sets. With the goal that we somehow need a probability that a specific combination of characteristics will lead to an acceptance of the offer, we choose the cross entropy as an error measure instead. The cross entropy compares an empirical with a theoretical distribution and returns not only the class assignment, but also the probabilities that a combination of characteristics belongs to one of the two classes. We can interpret this probability as the probability of acceptance.
There is another peculiarity within our task: acceptance probabilities should not fall with rising prices, all other things being equal. We therefore need a monotonicity criterion which ensures that if a characteristic increases, the target value also increases or at least does not decrease (this also applies to decreasing characteristics).
One method that fulfills all of the above requirements is a deep lattice network, which I described
in another post in this blog
in another post in this blog. After training the network, in which values are estimated for the variable parameters of the model on the basis of training data, the available information on a current offer, including the current price, can be used as a basis for the calculation. of the offered price and incl. information about the potential customer, a probability of acceptance can be estimated. If the price is varied while other characteristics remain constant, the acceptance probability is extended to a price sensitivity curve. I will present an example of the application in another post in this blog in this blog.
The curve must be used to decide what probability of acceptance is expected from the offering company. Let us return to the example of the service company that places orders with tradespeople. If, for example, you assume an acceptance probability of 50%, the craftsman will accept 50% of the order and reject 50%. If you want to increase the probability of acceptance (e.g. because there are only a few tradespeople with the required qualifications or because the tradesperson is known from experience to deliver work of a very high quality), the price and thus the probability of acceptance must be increased. On the other hand, you may be lucky and the tradesman is currently underutilized and accepts the job even if the price quoted has a 40% probability of acceptance. We are therefore dealing with an optimization problem here, which we have solved, for example, in a research project funded by the mFund using artificial intelligence approaches.