g  e  n  u  i  n  e  i  d  e  a  s
  home   art and
writings biography   food   inventions search
back to the future comparison tool


This tool implements the Back to the Future analysis, by comparing two funds/stocks/ETFs over a period of five years at the resolution of one data point per week. Historical data feeds are accessed from the Google finance database, while Google spreadsheets power the calculation and generate the plot. Just fill in the two boxes with your choice of stock or fund symbols, hit "SAVE", and this web page will reload with the results (The jagged curves are total returns from any single investment date to the present. The light smooth curves are effective, yearly percentage returns from that date to the present. You can roll over the chart and the caption will reflect that date's performance).


Now analyzing these stocks: t and HP


But there are limitations with any free tool:

  • Google spreadsheets are actually pretty fast. This calculation takes under five seconds. But, they don't offer selectively unlocked data entry cells, so I can't post the actual sheet. The alternative is publishing a locked spreadsheet graph to the internet.
  • Unfortunately, Google also throttles published graph updates to about one per 2 minutes. After choosing your investment symbols and pressing save, this page will reload with the OLD comparison. Just wait between 2 and 5 minutes (sigh), and the correct, updated plot should appear below.
  • Java script must be enabled.
  • Historical data is spotty, and the closing price is sometimes unavailable or reported on varying dates. Missing datapoints are bridged, and the two curves are aligned in time.
  • If the stock or fund hasn't existed for at least five years, the tool will not generate a plot.
  • I average the most recent month's stock price to set the baseline for return calculations- this moderates the effect of an aberrant day's gain/loss, and corrects for missing Google data.
  • The plot below was generated by the most recent user of this tool- don't use this tool if you are worried that others will free-ride on your brilliant stock selection.
  • Also, only one person can choose a pair of stocks at a time, so its possible someone else might be selecting and plotting different funds simultaneously, resetting the two minute clock....
  • This tool is a bit flaky and occasionally misfires (Google spreadsheets are still relatively primitive, so I had to code around many of its current limitations). USE AT YOUR OWN RISK.


If the plot is flawed or if it seems like Google is taking forever to finish the calculation, try a different pair of stocks/funds. And perhaps wait a few more minutes.

Contact Greg Blonder by email here - Modified Genuine Ideas, LLC.