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.
Today (3/22/2012) the interest rate on the EE series savings bond is 0.6%. There was no way that an interest rate of 0.6% could lead to doubling of the value of a bond in 20 years. In fact, the value of the bond would increase less than 15% over the 20 years. The effective interest rate on EE Series savings bonds had to be a lot more than 0.60%. Using semi-annual compounding over 20 years, a $1000 bond will become $2001.60 (double in value) with an interest rate of of 3.5%.