Hello, I have used your website for a great deal of research and it is an EXCELLENT resource. i have an issue I am struggling with understanding. As it relates to Weighted Average Life, I have seen this defined many ways from many sources. Some say it is the average time for a dollar of principal to be repaid/(or remain unpaid) and others say the WAL is the number of years until the principal is paid. This seems to be conflicting to me. I read on a reputable website that if you calculated WAL of a 30 year fixed rate mortgage to be 20 years, that is equivalent to a 20 year bullet. I don’t full understand how that is. The bullet will be paid off in 20 years however the principal balance on the mortgage wont be paid of in 20 years. 20 years is just the average time of time principal remains outstanding. I truly appreciate you clearing this up for me. It means a lot to have your time. I also am having trouble going from a CPR to WAL, I have been taught 1/CPR = WAL. Which seems to be true however when I use that same methodology to convert SMM in WAL and then divide by 12 months. I get a lesser WAL.

Again thank you so much for your time!

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]]>Again thank you so much for your time!

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]]>x[1], …, x[4] = # of people who die in 2013, …, 2016, respectively

x[5] = # of people who die in 2017+

For example, the solution to the puzzle as stated is x=(70, 20, 5, 2, 3)

Now suppose that we allow the life expectancy in 2012 to vary, but hold all other puzzle parameters fixed. Then there are exactly two additional puzzles which admit a solution:

2012 Life Expectancy = 2.2 with solution x=(40, 40, 10, 4, 6)

2012 Life Expectancy = 2.8 with solution x=(10, 60, 15, 6, 9)

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]]>https://welltemperedspreadsheet.wordpress.com/2012/10/01/a-new-way-to-visualize-numbers/

It was animated for me by Matt Henderson, a master of visual math. His blog is blog.matthen.com

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