[Avodah] How does Prozbul work?

[Eli Turkel via Avodah]

from wikipedia <https://en.wikipedia.org/wiki/Prozbul>

    Thus, if one would agree that shmita does not apply when Israelites
    are dispersed,[6] Hillel, great as he was, would not have changed
    a law of the Torah in order to fit the needs of his time. He and
    his beth din would have enacted a rabbinic exception to a rabbinic
    law. As the Rambam notes in Shmita V'Yovel chapter 9, when most Jews
    again live in the Land of Israel and the observance of the sabbatical
    and jubilee years are Toraitic commandments, the prozbul will no
    longer be able to be used. According to this theory, Prozbul, like
    `eruv <https://en.wikipedia.org/wiki/Eruv>, is a rabbinic exception
    to a rabbinic enactment. Prozbul cannot be used to get around the
    Torah commanded shmita and yovel, just as `eruv cannot be used to get
    around the fact that Torah prohibited carrying in the public domain.

I recently saw the opposite question: There are many ways to avoid the
problem of shmitta annulling laws without resorting to prozbul. One simple
example is to make the loan end immediately after RH of this year. There
are many other options. So the question is why the need for prozbul The
only answer I saw was that the general population was not aware of the
alternatives or else they were too cumbersome


[Email #2]

> In an article reviewing this shmitta, Rav Melamed threw in monkey wrench
> that I had never heard before. In calculating the numbers of Jews, the
> true number (at least as far as shmitta goes) includes all those people
> who are Jewish through maternal descent. Therefore the number of Jews is
> much higher than we believe it to be.

I have no idea how R Melamed got his numbers. RAL seemed to hold that
once a few generations have passed that a family has no connection with
yiddishkeit then the family would no longer be halachically Jewish even
for direct maternal descendants.

i.e. if someone could prove they were a descendant of shevet ephraim
through a direct maternal link the person still would not be Jewish.

I would assume that a descendant of annusim would be Jewish since they
kept their Jewish identification through various customs

-- 
Eli Turkel