1) I think this is a question on Rashi Bechoros 5b DH veHa who writes that in the days of Yechezkel they added a sixth. Howwever, at first sight it seems that according to Rashi they added on the Maneh, not on the Shekel. At any rate this is the opinion of Rabeinu Tam in Tosfos Bechoros 5a DH HaShekel that in the time of Yechezkel they added a sixth on the Maneh. However, Tosfos Bava Basra 90a DH veHaShekel writes that according to RI, Yechezkel added 4 Gerah onto the Sela. Originally the Shekel was 20 and he added 4 Gerah.

Malbim to Yechezkel 45:12 writes that Yechezkel's institution was that the Nasi should receive a larger portion.

That is all I have managed to find out so far and I must close now due to lack of time.

2) I learnt, bs'd, the above Malbim. The key verse is Yechezkel 45:12 "And the shekel is 20 Gerah". We must know a little about the background to this verse. Slightly before, verse 9 states "Thus says Hash-m Elokim 'It is enough for you the Princes of Israel; remove your exploitation and robbery....'". Verse 10 states "You should have fair balances....". Then verse 12 states about the Shekel being 20 Gerah and other details about the Shekalim. Verse 13 discussesthe Terumah that the Nasi receives from produce of wheat and barley. Tosfos Kidushin 41a DH Toreim writes [by the way, this is a Tosfos that is frequently learnt nowadays by kids in Talmud Torah and Yeshivah Ketanah, since it comes in the middle of the famous sugya of Shelichus at the beginning of the 2nd chapter of Kidushin - DB] that we derive from this verse that the obligation is to give one sixtieth (1/60) of the produce as Terumah.

3) Malbim explains verse 12 about the coinage. We are told in the verse about 20 shekalim, 25 shekalim, and 15 shekalim. This is a total of 60 shekalim and the pasuk says that this is a Maneh, which is 240 gold coins. Malbim writes that before Yechezkel's reform the Maneh was worth 200 zehuvim. He added a sixth onto the Maneh. This seems to follow the opinion of Rabeinu Tam in Tosfos Bechoros 5a DH HaShekel that Yechezkel only added on to the Maneh and it was only a lot later on that the Chachamim added to the Shekel. This also fits in with Rashi Bechoros top 5b who does not write anything about adding onto the Shekel; only to the Maneh.

Now the Maneh became 60 Shekel and, as we saw above, the Nasi does not receive more than 1/60. This is what Malbim means when he writes that the Takanah of Yechezkel was that the Nasi receives a portion of one sixtieth of a Maneh, which is 1 shekel. So, what I wrote in my first reply; that the Takanah was that the Nasi should receive a larger portion; is not correct. On the contrary, Yechezkel's aim was that the Nasi should nor receive too much. He wanted to make sure that the Nasi should not receive more than a Shekel.

This was because, up to now, the rich had been robbing the poor and Yechezkel's purpose was to protect the ordinary people.

4) Chazon Ish appears to say that Yechezkel added to the Shekel in oder to keep the real value of the Shekel similar to what it was at the time the Torah was given:-

Chazon Ish Yoreh Deah 182:6 (first paragraph) seems to give an explanation that is very different to that of the Malbim.

Chazon Ish cites RI (this is quoted in Tosfos Bava Basra 90a DH veHaShekel) that it was in the days of Yechezkel that they added on to the Shekel. CI writes that at that time "they added on to the shekel in the world". The inference is that there was some kind of global monetary reform at that time. The proof for this is what Shmuel said; in Bava Basra 90a; that "one may not add on to measurements more than one sixth, and one may not add on to the coin more than a sixth". At bottom 90a Rav Chisda states that Shmuel's source is the verse in Yechezkel.

I am not sure what is the correct Pshat in the Chazon Ish, but I hope what I write below, bs'd, is not too far off the mark. It seems to me that Shmuel is referring to a scenario where they want to add onto the measures and coins for financial reasons [this assumption can be supported by the context where Shmuel is cited; in the middle of a sugya about correct wights and measures]. This may well be because of inflation as you suggested, Yishai. If so, there is probably some general, possibly global, or at least regional, reason for this financial change.

But Shmuel provides a source for his Halacha from Yechezkel. This suggests that Yechezkel also had a financial motive. CI writes that the financial motive went hand-in-hand with the need for standard coins for the Dinim of the Torah. He writes that when the Chachamim saw it necessary to add on to the measurments they also added on to the coins of the Torah, so that the Takanah of Chazal should stand firm, and so that it should not be cumbersome for the public to have to make their calculations.

I think that what CI means is that since the weights and measures changed, the coins of the Torah also had to change so that the real, purchasing, value of the Shekel would be similar to how it was at the time the Torah was given. This way people would not have to make new calculations. If the weights went up then the shekel also to had to get bigger accordingly.

5) The Netziv from Volozhin writes that, according to Rabeinu Tam, those in financial control of the nation added to the coins whilst according to RI it was an addition for spiritual purposes:-

I found, bs'd, in Ha'amek She'elah; by the Netziv; on Sheiltot of Rav Hai Gaon 117:1, a fascinating analysis of this topic.

He cites Tosfos Bava Basra 90a, that we have seen a few times already, that according to Rabeinu Tam the Sages in the time of the second Beis Hamikdash added on to the Sela, whilst according to RI it was Yechezkel himself who made the addition.

The Netziv writes that it is known that there was no major change in the political running of Eretz Yisrael in the time of the Prophet Yechezkel. If Yechezkel instituted a change it is not possible that he made a change in the financial structure because this realm was not in his control; it was in the control of the king. Therefore we have to say that Yechezkel only added on to the holy Shekel; not to any mundane coins.

6) Rabeinu Tam adopts a different approach. He holds that adding on to coins is something dependent on those who control the economic aspect of the country. R. Tam writes that in the time of the Bayis Sheni it was the Chachamim who ran Eretz Yisrael, so they could change the coins.

[It was a big chidush to me what Netziv writes that the order of the state was in the hands of the Chachamim in the time of Beis Sheni. However I then remembered what the Droshos Haran writes, in the 7th Drush DH Aval l'Da'ati HaParsha HaZot, that the kings of Israel in the Beis Sheni did not possess kingship in their own rights; they were merely officers working for the kings of Persia and Rome and others. åäîìëéí àùø îìëå ááéú ùðé ìà äéúä îìëåúí îöã òöîí ëìì àáì äí ëô÷éãéí ìîìê ôøñ åøåîé åìæåìúí îï äîìëéí

According to this the kings of Israel in the 1st Beis Hamikdash were far more powerful than those in the 2nd Beis Hamikdash. We can state further that whilst the real power over Eretz Yisrael was in the hands of the foreign kings, nevertheless it is likely that the internal matters were run by the Jews, and it was the Chachamim who were in control of this, as we find in the first chapter of Pirkei Avos, from Mishnah 4 onwards, about the Zugot; the Nasi and the Head of the Beit Din - DB].

So according to Rabeinu Tam it could well be economic factors, such as inflation, that were the motive to adding to the coins.

They may have added on to the coin because the standard of living improved:-

7) Before I go further, bs'd, I want to make a diyuk that may support the above Netziv. I have suggested above that Rashi Bechoros top 5b apears to support Rabeinu Tam in his argument with RI concerning when the shekel was added on to. I point out now that both Rashi; second line 5b; and Rabeinu Tam cited in Tosfos 5a, write that the addition was made "in the days of Yechezkel". This suggests that it was not Yechezkel himself who made the addition and supports the Netziv that it was the king who was responsible for these matters then; and he added on to the Maneh. In contrast, Tosfos Bava Basra 90a writes in the name of RI that Yechezkel himself added on to the Shekel, which again supports Netziv that Yechezkel added specifically on to the holy Shekel; and not on to other coins; which were not in his sphere of activity.

8) We have suggested above that the addition on to the Shekel may have been, according to some Mefarshim, because of inflation and the need to keep the coins of the time similar to their purchasing power at the time when the Torah was given, so that the coins of the Torah would conform with the contemporary coins. However, I found another possible reason mentioned why the coins were made bigger. This is by Rav Chaim Greineman, zt'l, in Chidushim uBiurim Bechoros 50a DH Sham uMinayin She-Im Rotzeh. He suggests that people may have generally become richer. If so, the Shekel of the Torah may have still been able to purchase what it purchased at the time of the Torah, but that would now not be considered such a siginficant purchase by most people because they had become accustomed to buying more goods of a higher quality. Therefore, the Shekel was made bigger, so that its increased weight in silver was capable of buying more.

The shekel got bigger but the Gerah remained the same:-

9) Now to conclude this topic.

We have seen a number of explanations about who added on to what coin, and when and why, but to finish off I want to come back to what you wrote, Yishai, that if a bushel of grain used to cost 6 old shekels (6x20= 120 gerah) then after the change it would cost 5 new shekels (5x24 = 120 gerah).

This is not the case because what in fact happened is that the shekel became bigger. In those days coins were actually worth their weight in gold, silver and copper. The Gerah was a fixed coin. Rav Chaim Greineman, writes in Chidushim uBiurim Bechoros 50, that we learn from the verse in Shemos 30:13 "The Shekel is 20 Gerah" that the gerah is a fixed amount but the shekel changes. So, if there was inflation, a bushel of grain used to cost 120 gerah = 6 shekel and now it costs 144 gerah = 6 shekel. The gerah coin remained the same and the shekel was made bigger and heavier and was now 24 gerah, so it was capable of buying the same amount of grain.

This is stated in Tosfos Bechoros 5a DH HaShekel, that to start off with the Shekel was 20 and now became 24.

And, finally, we must conclude that the inflation in the time of Chazal was nothing like the inflation of 1986. Shmuel says, in Bava Basra 90a, that one may not add on more than a sixth to a coin.

Dovid Bloom