Rule of 72

This is interesting.

Say, if I have $100, and the saving account rate is 2%. Assuming compound interest, how long does it take to double the money?

An easy way to estimate that is to simply calculate: 72 / 2, which is 36. So it will take 36 years to double my money.

Really? Let’s see… 100 * (1+0.02)^(36) = 100 * 2.0398… = 203.98 !!! WTF !!!

How about SPY? Based on trailing 10-year data, the fund generated average annual returns of 11.04%. So how long does SPY take to double my money? 72 / 11 = 6.54.

OK, just 6 and a half year. That’s all it takes. =)

Now you know how to do these kinds of estimates.

The math behind this shortcut is actually quite simple: https://web.stanford.edu/class/ee204/TheRuleof72.html

Covid-19 tests

Apparently there are 3 types of Covid 19 tests.

1. Nucleic acid amplification tests (molecular tests)
– also known as genetic, RNA or PCR tests.
2. Antibody tests – also known as serology tests.
3. Antigen test

Diagnostic or PCR test. This is the one with the long stick getting mucus from your nose. Even though it takes a few days for the virus to replicate in the nose, this method is so far the most reliable one.

Antibody test. This is a blood test to look for antibodies to the virus. Since it takes time (at least 4 days) for your body to generate antibodies, and without FDA authorization, the result may not mean much.

Antigen test. This method tries to detect proteins from the virus in nose. It is a quick screening test for just a few minutes, but accuracy is still to be determined.

ref:
https://asm.org/Articles/2020/April/COVID-19-Testing-FAQs
https://www.npr.org/sections/health-shots/2020/05/01/847368012/how-reliable-are-covid-19-tests-depends-which-one-you-mean

WordPress hosting on AWS

I am glad my blog is on wordpress.com.

EVwf9tRUMAATNy1

Seems like there are better ways now (not necessarily easy):
https://aws.amazon.com/getting-started/hands-on/launch-a-wordpress-website/
https://docs.aws.amazon.com/elasticbeanstalk/latest/dg/php-hawordpress-tutorial.html

Unemployment

The number of Americans who applied for unemployment benefits last week rocketed to a record 3.28 million

Screen Shot 2020-03-26 at 10.42.40 AM

Why is the market still going up? Don’t fool me. People don’t have jobs, government is printing money, where are we going? This is probably just the first wave of unemployment numbers, wait until the next wave.

Link: https://www.marketwatch.com/story/a-record-328-million-americans-applied-for-unemployment-benefits-last-week-due-to-coronavirus-2020-03-26

Social distancing?

Would social distancing work? The available hospital beds line is way down there. I kinda understand now why China built new hospitals in 7 days and locked down cities. It was really to minimize casualties. Social distancing could only delay the spike. I wonder if we spent the trillion dollars to pay everyone to stay home instead, would that be a better alternative.

Screen Shot 2020-03-26 at 8.28.42 AM