You have to put the limit somewhere, anything else than splitting in half seems very tedious. Besides groceries is just one example of many expenses so I believe that differences get averaged out, and if they don't the two of us don't care about it.
My partner and I don't do this any more - especially now that we are married - but for the first couple years we lived together we split the grocery bill using a 1 to 0.77 ratio we derived from our bodyweights.
We just derived the ratio once and never updated it - neither of us were particularly invested in losing, gaining, or tracking our weight - so it seemed an OK proxy metric to handle the fact that we ate noticeably different amounts.
A few years later we've started to consider the fact that we might both be on the spectrum :)
> Besides groceries is just one example of many expenses so I believe that differences get averaged out, and if they don't the two of us don't care about it.
Yes, that is where I was going with my line of questioning. What is the point of all that separating work if you don’t care about it not averaging out?
What I am saying is that when we buy a new sofa we split the expense in two halves, we don't measure each second each of us spend sitting on it so that the split represents EXACTLY our individual usage. Same with groceries, we don't count each grain of rice each of us consume, we are okay with some level of inaccuracy. Anything besides that would be absolute madness.
At the end of the month we still both get a pretty solid idea of our individual expenses no matter who actually paid of an item. For instance my expenses for the month are ¥2200 while last month it was ¥2500, seems like useful data, right? Who cares if one of us made a better deal than they should have on the sofa while the other consumed a few grams of rice more than other?
I am surprised this inaccuracy makes you question the reason of tracking personal finance.
Edit:
> What is the point of all that separating work if you don’t care about it not averaging out?
Maybe that's the source of the confusion, our finances are already separated, there is no extra work separating expenses. There is extra work for expenses we have in common like the sofa or groceries, in which case we do half and half even if that's sometimes inaccurate.
I can imagine that splitting the expenses is symbolic for some couples, more than anything else. Sometimes because history (e.g., didn't feel like an "equal partner" in a previous relationship). And for others, it might just be customary, or seem sensible.
My situation has been different than that, in that I wished my GnuCash setup didn't incidentally quantify some categories of expenses so well. I've adjusted some categories since then. (Though it did make me think of a line of awful dialogue, for the worst rom-com jerk character ever.)
Does splitting here mean each person pays half of the price of the shared item? If so that puts more pressure on the lower earner. One approach would be to put both incomes in a big pot, take all the shared expenses from that pot, and then divide and distribute the rest between the two.
Me and my wife kind of do this. More specifically we contribute to family expenses proportionally to our income and we pay all family expenses from a shared bank account (fed with monthly contributions).
Any personal expense is paid by our personal account.
This guarantees that we do have the same saving rate and this feels to me much more fair that a 50/50 split.
We started with something like this as well. The problem is that the savings and disposable income will also be proportional. If the difference in salaries is large then it could seem unfair. But then again it depends whether you view wealth as an individual or shared affair.
We do have pretty different incomes and working hours. Wealth is absolutelly a shared affair, but we could not get to agree on how to invest the savings. We have pretty different risk tolerance and asset class affinity, so we decided to split proportionally and grant each other freedom with whatever is not necessary for the family needs.
Most likely we'll re-evalute the criteria in the future if absolute value of our savings diverge too much or if our investing choices will have markedly different ROIs.
