"would be decreasing" is a correct and usable phrase in written English.
It is used to talk about a potential future decrease in something. Example: If we continue to use fossil fuels at the current rate, our natural resources would be decreasing rapidly.
If it were not for immigration, the city's population would be decreasing today.
"It would be decreasing the size of the pie to increase the size of some slices," says MIT economist David Autor.
It was hard to control my incredulity as I explained that, in fact, his taxes would be decreasing, not rising.
If the server is not able to provide additional streams any more, the bandwidth for each stream (and for all streams summarized) would be decreasing.
The cervix, I was told, leads to greater sexual satisfaction and that by taking it out, I would be decreasing my ability to enjoy sex with my husband.
According to Levin regarding the large surge in recruits, "the reason that that happened was that Afghan leaders realized that President Obama was serious and meant business -- that commitment here [in Afghanistan] is not open ended and that we would be decreasing troops in July 2011".
The levels of noradrenaline and 5-HT would be decreased.
Water deliveries would be decreased based on how far water levels drop in Lake Mead and Lake Powell.
He recently decided that the administrative budget, close to $300 million, would be decreased by another $100 million.
The performance of modified models using relevant modified coefficients would be decreased to a certain extent.
Moreover, both values and standard deviation of the preexponential factor (A) would be decreased due to the presence of limestone.
