Predicting StockX Sneaker Prices With Machine Learning

Published in

The Startup

6 min readOct 2, 2020

Photo by Arun Krishnavajjala on Unsplash

The Footwear industry consists of companies engaged in the manufacturing of footwear such as dress shoes, slippers, boots, galoshes, sandals and athletic and trade related footwear; however, the most lucrative sector of this industry is collectible sneakers. The rise of marketplace apps like StockX and GOAT, alongside the proliferation of social media sites where you’re just one message away from turning a rare pair of trainers into cash, mean that more people are selling their shoes than ever before. The global sneaker resale market has been valued at over $2 billion, while the right pair of kicks can go for over $10,000 💸. Moreover, the massive margin of profit for each shoe makes the resale market attractive to those who would like to make some extra cash, given that in the past year, the average profit margin in the sneaker industry was 42.5%.

While there is plenty of money to be made, it can be risky to buy a shoe due to the volatile nature of each shoe. Sneakers are like stocks with their resale price constantly changing from day to day. Thus, I developed this web application to predict the price of a given shoe based on factors such as date, shoe size, buyer region, and more.

This tool resolves the issue of knowing which sneaker is worthwhile and when to buy it. As a “sneakerhead” and reseller myself, I know that this program will have lots of value in the community.

For in-depth details on this project, check out my GitHub Repo.

Getting Started

Installation

Clone this repo, create a blank Anaconda environment, and install the requirements file.

# Clone the repo
$ git clone https://github.com/lognorman20/stockx_competiton# Create new environment called ‘stockx-env’
conda create -n stockx-env python=3.8# Activate the environment we just made
conda activate stockx-env# Install the requirements
pip install -r requirements.txt

Usage

In your terminal, Cd to the repository, then to the application folder. Run this program using the command below. Make sure to run the app from the `application/` directory. After running it, click on the link provided in the terminal.

cd application
python app.py

Understanding the Data

The data I used is from StockX’s data competition in 2019. Here’s a description of the data from StockX:

“The data we’re giving you consists of a random sample of all Off-White x Nike and Yeezy 350 sales from between 9/1/2017 (the month that Off-White first debuted “The Ten” collection) and the present. There are 99,956 total sales in the data set; 27,794 Off-White sales, and 72,162 Yeezy sales. The sample consists of U.S. sales only.

To create this sample, we took a random, fixed percentage of StockX sales (X%) for each colorway, on each day, since September 2017. So, for each day the Off-White Jordan 1 was on the market, we randomly selected X% of its sale from each day. (It’s not important to know what X is; all that matters is that it’s a random sample, and that the same fixed X% of sales was selected from every day, for every sneaker). Every row in the spreadsheet represents an individual StockX sale. There are no averages or order counts; this is just a random sample of daily sales data.”

I did some exploratory data analysis and made some visuals. You can check out my EDA notebook on the GitHub repo:

Fig. 1: The Average Daily Sale Price from 2017 to 2019

Fig. 3: The Average Sale Price by Sneaker Name

Fig. 4: Coorleations between each feature

Fig. 5: Sale Price Distribution of Off-White Sneakers

Fig. 6: Sale Distribution of Yeezy Sneakers

Fig. 9: Best Selling Sneaker Retail Prices

Development

Data Cleaning

The data that StockX gave me was not very messy. Here’s what I did:

Changed ‘order date’ dtype
Changed ‘release date’ dtype
Removed ‘-’ from sneaker name
Removed ‘$’ and comma from sale price
Removed ‘$’ from retail price
Renamed columns to get rid of spaces
Converted dates into numerical values
Converted categorical data to numerical using OneHotEncoding

Model Building

To begin, I split the data into train and tests sets with a 80/20 split.

I selected three models:

Random Forest Regressor because has the power to handle a large data set with higher dimensionality, provides higher accuracy through cross validation, is commonly used when analyzing the stock market due to its random nature, and each tree draws a random sample from the original data set when generating its splits, adding a further element of randomness that prevents overfitting.
XGBoost because I have a large number of training examples given that this dataset is has about 100,000 rows. Therefore, it should have plenty of data to learn from and apply gradient boosting. This dataset also has a mix of categorical and numerical features, which XGBoost tends to do well with.
Decision Tree Regressor as a baseline model to compare the others to.

Model performance

Since I am trying to predict an exact value, I decided to use mean squared error to measure the accuracy of each model. I was expecting XGBoost to perform the best due to its gradient boosting methods, however, the random forest regressors was able to out perform it.

Decision Tree Accuracy (Baseline): 0.97284
XGBoost Test Accuracy: 0.98225
RandomForest Test Accuracy: 0.98452
Model with best accuracy: RandomForest

The highest performing model was the RandomForestRegressor with an accuracy of 98.5%. Not bad.

Productionization

In this step, I pickled my model and saved it into a callable object to be used to create a basic Flask application.

After that, I struggled to summon my knowledge of HTML and CSS from my 6th grade tech class to create a simple front-end web site for my model to be hosted. I inserted my model into the web application and the rest is history! (Check out the demo on the GitHub page)

Reflection

Real World Application

This project can be applied in several ways.

1. Helping to decide when to buy a sneaker by predicting its price at any given time 📈
2. Knowing which factors influence the sale price of each sneaker can help businesses optimize their shoe buying process to those that have the most potential 👍
3. Sneaker businesses can see a timeline of when sneaker prices are high or low to know when to buy/sell 📆
4. Know if your friend got ripped off for buying their shoes too early or too late! 🤣

What I learned

All in all, this project gave me better insight into the worlds of machine learning and sneakers.

If I was to do this project again, I would choose a different way to handle categorical variables other than OneHotEncoding such as ` pd.get_dummies` to reduce the amount of features. When I was creating the Flask application, it was difficult to recreate the lucrative amount of features that I had from my training data in a real world application, and using a different method would absolve this issue.

I was surprised that Off-White sneakers typically sold for much more than Yeezy sneakers. From my experience as a sneaker reseller, this threw me off guard. Moreover, I was surprised to see that certain retail prices typically sold better than others. Visualizing the data helped me notice these trends and I now know how I can apply them.