Title says it all... pretty much.
Maybe this exercise is really simple and this question a bit silly: I'd guess it's simply the sum of all expenses (i.e. expense accounts) over the sum of all income, per time period, e.g. per year (1 Jan - 31 Dec). But happy to get some ideas / comments on how to think about it / what steps are involved in establishing it via GnuCash...
Related resources:
What is the Savings Rate?
The savings rate is a measurement of the amount of money, expressed as a percentage or ratio, that a person deducts from their disposable personal income to set aside as a nest egg or for retirement.
In economic terms, saving is a choice to forego some current consumption in favor of increased future consumption, so the savings rate reflects a person or group's rate of time preference. The savings rate is also related to the marginal propensity to save.
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The savings rate is the percentage of disposable personal income that a person or group of people save rather than spend on consumption.
- https://www.investopedia.com/terms/s/savings-rate.asp
- How exactly do I determine my savings rate?
- https://savology.com/savings-rate-what-is-it-and-why-is-it-important
- https://forum.mrmoneymustache.com/ask-a-mustachian/saving-rate-is-is-gross-or-net/
- https://www.thebalance.com/what-is-the-savings-rate-5198647
- https://www.cnbc.com/2017/07/17/savings-rate-formula-will-show-you-how-close-you-are-to-retiring-early.html
- https://www.gnucash.org/docs/v4/C/gnucash-guide.pdf
- https://lists.gnucash.org/pipermail/gnucash-devel/2012-April/033843.html ("Savings Rate Report")
- https://news.ycombinator.com/item?id=12025912 ("your savings rate, as a percentage of your take-home pay")
- https://networthify.com/calculator/earlyretirement
- https://www.mrmoneymustache.com/2012/01/13/the-shockingly-simple-math-behind-early-retirement/
- https://github.com/BenBergman/gnucash-custom-reports/blob/master/savings-rate.scm
- https://www.gnu.org/software/guile/manual/guile.html#Lambda
- https://www.gnucash.org/docs/v4/de/gnucash-help/report-create.html
- https://wiki.gnucash.org/wiki/Custom_Reports#Language_details