Introduction:
One common analysis in business intelligence is comparing data over different time periods, such as Year-Over-Year (YOY) comparisons. YOY analysis helps in understanding how a particular metric or measure has changed from one year to the next.


Understanding YOY Analysis:

Year-Over-Year (YOY) analysis is a method used to compare data from the current year with the same period in the previous year. It is a valuable technique for identifying trends, seasonality, and performance changes in your business. YOY comparisons can be applied to various business metrics, such as sales, revenue, profit, or any KPI you want to assess over time.


Calculating YOY in Power BI:

To calculate YOY in Power BI, follow these steps:

Data Preparation: 
First, you need to ensure your data includes a date column. This is crucial for time-based comparisons. In Power BI, you should load your data into the data model and create a date table.

Create a Measure:
In Power BI, create a new measure that calculates the value you want to compare


YOY.

YoY Sales =
VAR CurrentYear = YEAR(TODAY())
VAR LastYear = CurrentYear - 1
RETURN
CALCULATE(
SUM('Sales'[Sales]),
FILTER(
ALL('Date'),
YEAR('Date'[Date]) = LastYear
)
)

Visualize the Data: 
Now, you can use this YOY measure in your visualizations to see the YOY comparison for your selected metric.

Calculating YOY% in Power BI

To calculate the Year-Over-Year percentage change (YOY%) in Power BI, you can use the YOY measure created above and build upon it. Here's how:

Create a Measure:
Define a new measure for YOY% as follows:


YoY % Sales =
VAR CurrentYearSales = SUM('Sales'[Sales])
VAR LastYearSales = CALCULATE(
SUM('Sales'[Sales]),
SAMEPERIODLASTYEAR('Date'[Date])
)
RETURN
DIVIDE(CurrentYearSales - LastYearSales, LastYearSales)

Visualize the Data: 
Now, you can use the YOY% Sales measure in your visualizations. This measure will display the percentage change between the current year and the previous year.


Conclusion:
Calculating YOY and YOY% in Power BI is a fundamental technique for understanding how your data has evolved over time. By creating measures and visualizations, you can gain valuable insights into your business metrics and make informed decisions based on the year-over-year comparisons.