Calculate percentage betwwen two months

I would like to calculate the percentage increase of some data in the database between two months. But as much as I think about it, I can’t find the aggregate.

Id: 12548
name: jhon
expence: 200$
day: 22-3-2022

id: 15426
name: mary
expence: 150$
day: 15-4-2022

more or less
calculate increase percentage between two month

{
    $setWindowFields: {
      partitionBy: {“$month”:”$day”},
      sortBy: { day: 1 },
      output: {
        sumExpence: {
          $sum: "$expencel",
          window: { documents: [ -1, 0 ] }
        },
        previousDateTime: {
          $push: "$date",
          window: { documents: [ -1, 0 ] }
        }
      }
    }
  }

Something idea??
thank you