Yesterday I went looking for free historical data for small cap companies only to find the Yahoo! Finance API had been turned off more than a year ago. Hmm, well on to Google Finance then… also turned off their API sometime in 2018. Darn, this was supposed to be a quick project.

The idea was to illustrate the power law of stock price growth: Around 15% of all a portfolio drives 85% of its returns. I want to show how very small cap portfolio growth differs from large cap portfolios and if possible show how a small cap index fund’s performance differs from setting up a portfolio that starts as small cap (but you don’t sell when a company transitions to medium / large cap status.)

In my mind I can see an animated bar graph built from all the positions sorted by value , with each frame representing a month or year. Imagine going from 1970 to the present. You will see how the sum of the bars equals your portfolio’s value. Even though half your positions may be losers the unrealized losses are tiny compared to the unrealized gains. You could illustrate how an automatic rebalancing strategy potentially damages long term returns.

Searching out alternative stock data sources, I found a number that weren’t quite good enough: I need prices adjusted for splits and with dividends, preferably with a reinvested dividend price (there was one dataset with this feature I have seen.) Some other sources have data but with lots of errors.

Several other promising sources turned out to have shut down recently in addition to Google and Yahoo! This comment thread tells the story. Two sites were discussed there as alternatives, only to go dark over the course of last year.

Looking over the Ally Invest API I couldn’t find historical quotes of the sort I need; they have a very nice API for realtime stock and options data and trading though. I’ll follow up with Interactive Brokers.

There are two more free possibilities I’m going to investigate. If they don’t pan out I guess I’ll have to pay. Oh well.