A long long time ago there was a product called Lotus Improv. Our premise was that complex spreadsheets were very difficult to maintain, to audit and to modify. So much so that we had heard stories about companies fearing making any change to the spreadsheets they run their business on.
Maybe the person who created the monster was no longer with the company or maybe the spreadsheet was so complicated (and untestable) that the benefits of making a change did not outweigh the risk of introducing an error. That was around 1987.
Here we are 25 years later and shockingly the situation seems to still be tolerated. From an article in MarketWatch:
"Such mistakes not only can lead to miscalculations in family budgets and distorted balance sheets at small businesses, but also might result in questionable rationales for global fiscal policy, as indicated by the case of a math error in a Harvard economics study. By failing to include certain spreadsheet cells in its calculations, the study by Harvard economists Carmen Reinhart and Kenneth Rogoff may have overstated the impact that debt burdens have on a nation’s economic growth." (from MarketWatch "88% of Spreadsheets have errors")
Improv has come and gone. It was ground breaking in its time, won some awards, but not the most important award, customer adoption!