The worry that BLR will go up and down over the long term, is why Islamic Financing with its fixed "profit" rate, has been gaining a lot of interest (pun intended).
When you consider, most people take long term loan (e.g. 30 years term), BLR can swing up and down, economy can swing up and down. Your income can also gyrate during these times...
From past few decades, the economy has been in roughly 10 year cycles,so for ppl having 30 yr loan, need to consider that every 10 years whether can keep up their monthly payment.

Those who makan gaji, their company they work for can go bust. Those in business will feel the downturn even more. Of BLR go up, spending will go down. Those with loans will suffer, and those without loan will hesitate to take loan (cos interest so high)....talking about effects of recession can fill up a whole book...haih...