Average Home Price and Count of Home Sales in the Bay Area (2015 – 2020)

For this project, I decided to make a series of data visualization implementations to analyze the real estate market of the bay area, for example, a comparison of the average value of homes from different cities, the trend of the value of homes from 2015 to 2020, etc.

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Goals

Who doesn’t have a dream home? So do I, and this is one of the biggest reason why I choose this topic as my final project.

Personally, as a computer science student in the bay area already, I think it is probable for me to consider buying a home in the bay area if I end up finding a job here one day in the future.

However, I have zero sense in the real estate market of the bay area at the moment and I don’t want to wait for the day comes that I have to ask for a real estate broker to tell me the story. Luckily, today, I have the opportunity to do some researches and visualize them in my project, I think it is helpful for me and those who may have the same consideration as me and want to better understand the market in advance. So this is why and where my curiosity starts.

About Location

The data of the whole United States is too big, so I want to focus only on the bay area, considering that it has one of the most valuable real estate markets and audiences. Besides that, it’s more related to me, since I personally live in the bay area and will likely keep living here for a while in the future. So, knowing this real estate data can also benefit me if I consider buying a home in this area.

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List of cities in the Bay Area

From https://en.wikipedia.org/wiki/Category:Cities_in_the_San_Francisco_Bay_Area

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Why is the Trend?

When an investor wants to invest a product, I think the most important questions to ask are is it a good price already and how many people will buy it. So I list the average price of the home price from different cities in the past 5 years and the total count of home sales in 2019 in order to make a trend and see if it raised or dropped so people know what might be the upcoming outcome.

Why a Map?

A map is also helpful because it’s easier for people to see the actual location of the data and find out the cluster of which cities have the similar data.

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About the dataset

Among the dataset, I chose the list of ZHVI All Homes (SFR, Condo/Co-op) Time-Series ($) by the city category and Monthly Home Sales (Number, Seasonally Adjusted) by the city too.

By the date I checked, this dataset has 27,539 rows and 293 columns and the file size is 63KB.

Some columns I would use

  • Region Name
  • State
  • Monthly Average Home Prices
  • Monthly Count of Home Sales

Home values

Zillow Home Value Index (ZHVI): A smoothed, seasonally adjusted measure of the typical home value and market changes across a given region and housing type. Zillow publishes top-tier ZHVI ($, typical value for homes within the 65th to 95th percentile range for a given region) and bottom-tier ZHVI ($, typical value for homes that fall within the 5th to 35th percentile range for a given region). Zillow also publishes ZHVI for all single-family residences ($, typical value for all single-family homes in a given region), for condo/coops ($), for all homes with 1, 2, 3, 4 and 5+ bedrooms ($), and the ZHVI per square foot ($, typical value of all homes per square foot calculated by taking the estimated home value for each home in a given region and dividing it by the home’s square footage). Check out this overview of ZHVI and a deep-dive into its methodology.

Inventory and sales

Zillow provides data on sold homes, including sales counts (for which there’s detailed methodology), median sale price and median price cut for various housing types,  and foreclosures provided as a share of all sales in which the home was previously foreclosed upon.

Home Types

  • All Homes: Zillow defines all homes as single-family, condominium, and co-operative homes with a county record. Unless specified, all series cover this segment of the housing stock.
  • Condo/Co-op: Condominium and co-operative homes.
  • Multifamily 2+ units: Units in buildings with 5 or more housing units, that are not condominiums or co-ops.
  • Duplex/Triplex: Housing units in buildings with 2 or 3 housing units.

Inventory and Sales

  • Median Sale Price ($): Median of the selling price for all homes sold in a given region.
  • Median price cut (%): Median of the percentage price reduction for homes with a price reduction during the month. Foreclosure Resales (%): The percentage of home sales in a given month in which the home was foreclosed upon within the previous year (e.g. sales of bank-owned homes after the bank took possession of a home following a foreclosure). Monthly Inventory: The count of unique listings that were active at any time in a given month.
  • New Monthly Inventory: The count of unique listings that were newly listed at any time in a given month.
  • Median Daily Inventory: Each Wednesday, daily inventory is calculated as the number of currently active listings. These counts are then aggregated into the number reported by taking the median across weekly values.
  • Age of Inventory: Each Wednesday, the age of inventory is calculated as the median number of days all active listings as of that Wednesday have been current. These medians are then aggregated into the number reported by taking the median across weekly values.
  • Days on Zillow: The median days on the market of homes sold within a given month, including foreclosure re-sales. The latest data is for one month prior to the current ZHVI (e.g., if the most current month for ZHVI data is January, the most current month for Days on Zillow data will be December).
  • Home Sales: The number of homes sold during a given month. Note: ZIP code sales data is not latency adjusted, but is filtered.
  • Home Sales, SA: The number of homes sold during the given month, seasonally adjusted using the X-12-Arima method. Zillow Home Value Forecast (ZHVF): The ZHVF is the one-year forecast of the ZHVI.

City Geocoding

Generate the geo-coordinates of latitude and longitude for each city, which I’ve done with a Google Sheet Adds-on, Geocode by Awesome

License

This dataset follow the terms of use provided by Zillow its own license, which can be found at Public Records Data Terms of Use Definitions

Data Encoding

Section Description
Map The whole map is a US county map, and the projection is the bay area. Circles represent a city in the area based on the geo-coordinates. Colors represent the count of home sales (2015 – 2020) and sizes represent the average home price (2015 – 2020).
Bar The X-axis is the average home price or the count of home sales of the city (2015 – 2020) and the Y-axis is the city names in the Bay Area. Color is the count of home sales.
Line The X-axis is years from 2015 to 2020 (price) or 2015 to 2019 (count), Y-axis is the average home price or the count of home sales. Color is neutral.
Legend Color is the count of home sales (2015 – 2020) and the size is the average home price.
Tooltip Detail on-demand panel provides information for an individual city, including the city name, average home price and count of home sales (2015 – 2020).

Map

Average Home Price and Count of Home Sales in the Bay Area (2015 - 2020) Interactivity1
Zoom

Scroll or double click on the map allows you to zoom-in and zoom-out.

Average Home Price and Count of Home Sales in the Bay Area (2015 – 2020) Interactivity2
Drag

Press your mouse and hold it allows you to move the map.

Average Home Price and Count of Home Sales in the Bay Area (2015 – 2020) Interactivity3
Hover

Mouse hover on the circle will highlight the circle and the matched city in the bar and also display the tooltip.

Average Home Price and Count of Home Sales in the Bay Area (2015 – 2020) Interactivity4
Click

Click on the circle or the bar will display the detail on-demand panel on the sidebar which provides information for the highlighted city.

Bar

Average Home Price and Count of Home Sales in the Bay Area (2015 – 2020) Interactivity5
Hover

Mouse hover on a line of the bar will highlight the matched circle and also display the tooltip.

Average Home Price and Count of Home Sales in the Bay Area (2015 – 2020) Interactivity6
Click

Click on a line of the bar will display the detail on-demand panel on the sidebar which provides information for the highlighted city.

Dropdown

Average Home Price and Count of Home Sales in the Bay Area (2015 – 2020) Interactivity7
Select

The dropdown menu allows you to switch different types of graphs, such as a bar for average price and line for average price trend.


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