It usually isn't wise to be preachy in the docs, but we could add a suggestion that proportional=True be used only when (0, 0) is known to be in the dataset and when it is in the same neighborhood as the other data points.  A reasonable cross-check would be to verify than a plain OLS regression would produce an intercept near zero.

    linear_regression(hours_since_poll_started, number_of_respondents, proportional=True)