This article has been adapted from specific stair and railing specifications that are similar among codes and countries (but not identical). -- IBC, IRC, BOCA, Kingston NY Stair Code, New York State Residential Building Code for Stairs (included here), Florida, Pennsylvania, New Jersey, & other sources.
Average APY. According to CNN Money, the average annual percentage yield on a savings account in the United States was just 0.06 percent in 2013. This means that if you nested away $100,000 in the average savings account, it would net you an additional $60 in interest over the course of one year.
Interest rates being paid to savings accounts are incredibly low right now (in fact, aside from a few specialty banks, you'll be lucky to get 1%), but in years past, 5-6 or even 10% wasn't uncommon (though you'd have to go a while back for that!). But in general, that's how interest/compounded interest works.