# Great People Points explained

Discussion in 'Civ4 Strategy Articles' started by Kylearan, Dec 6, 2005.

1. ### Kylearancompound eye

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There seems to be a lot of confusion about great people, how they are generated and the odds involved, so I thought I'd try to explain that a bit.

1. Generating Great People

Great people are generated by accumulating great people points (GPPs) in your cities. Every city has its own counter that keeps track of how many GPPs have been produced in that city already, which can be seen in the lower right corner of the city screen. Once a city has reached a specific threshold, a great person will be generated, and the GPP counter of that city will be reset to zero. This threshold is a civ-wide one, and will increase each time a great person is born so that the next one will be harder to get.

For normal game speed, you need 100 GPPs in one of your cities to generate your first great person. From then on, every great person thereafter will cost you an additional 100 GPPs until 1000, then the threshold will be increased by 200 for every great person, making it even harder.

So you need 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, then 1200, 1400, 1600, 1800, 2000, 2200, ... GPPs to generate a new great person.

For Epic game speed, you need 150% of the required GPPs, so it's 150, 300, 450, 600, ...

For Quick game speed, you need only 67% of the required GPPs, so it's 67, 134, 201, ...

Note again that the threshold is civ-wide and the same for all cities, while the GPP counter is individual for each city. For example, you have city A with 80 GPPs and +2 GPPs per turn, and another city B at 99 GPPs and +3 GPPs per turn. So city B will reach the threshold of 100 GPPs next turn. This will produce your first great person, and sets the GPP counter of city B back to 2 (2 excess GPPs are carried over). Additionally, the new threshold for producing a great person is set to 200, so city A, now at 82 GPPs +2 GPPs per turn, will need much longer than before to produce a great person!

For the question whether it's better to concentrate all your GPP production in one city, or spread it over multiple cities, see an article by Vol here.

Note that you will also receive specific great persons if you are the first to discover certain techs (Music, Economics, Physics, ...). This does not effect the threshold for your GPP production in any way. The same is true for great people generated by other civs: They won't effect your threshold either.

2. Sources for GPPs

Normally, a city won't produce any GPPs on its own. There are two sources to produce GPPs, specialists and wonders.

Specialists produce +3 GPPs per turn, except the citizen specialist which will produce none. Great wonders generally produce +2 GPPs per turn, and small wonders +1 GPP per turn. Once a wonder becomes obsolete, it will no longer produce any GPPs.

These GPPs per turn can be further boosted by "+x% birth rate" enhancers. The most obvious one is if you play a philosophical leader, which provides +100% birth rate for all cities. Then there's the Pacifism civic that comes with Philosophy, which adds +100% birth rate for all cities as well. Finally, there are some wonders that provide a similar bonus, like the Parthenon (+50% birth rate for all cities) and the National Epic (+100% birth rate for the city it was built in only). Note that these boni are additive, so if you are a Philosophical leader, have adopted Pacifism and have the Parthenon, you will get +250% GPP production in all cities.

3. Odds to Get a Specific Type of Great Person

There are five types of great persons: Engineers, merchants, scientists, prophets, and artists. The odds of which type of great person will be generated once one of your cities has produced enough GPPs, depends on which types of sources contributed to the GPP pool of that city. The odds can be displayed by mousing over the GPP bar in the lower right corner of the city screen.

Each type of specialist counts as one source for the respective great person type, and each wonder has noted in its description which type of source it is. For example, the Great Library counts as a source for great scientists, while the Parthenon counts as a source for great artists.

If you have produced only one type of GPPs in your city once it has reached the threshold, then you are guaranteed to get a great person of that type. For example, if your city has the Parthenon (source for great artists) and you had hired an artist specialist to increase GPP production, you will be guaranteed to get a great artist.

If you have different types of GPP sources, it gets a little more complicated. For each turn, the game notes what types of sources had produced GPPs in the city (regardless of how many GPPs each source had contributed!). This determines the odds of which type of great person would be produced for that turn. The overall odds are the average values of all the turns since the last great person was generated in that city.

Note that difference: The number of GPPs will determine when a great person will be generated, and the number of sources will determine what type it will be.

Examples:

* You have the Parthenon (great artist source) and a priest specialist (great prophet source) in the city the whole time. Your chances will be 50% to get a great artist and 50% to get a great prophet. Note that it's irrelevant that the Parthenon produced only 2 GPPs while the priest produced 3 GPPs per turn; they both count as one source.

* A city has the Great Library (great scientist source), an engineer, and an artist specialist, plus the two free scientist specialists from the Great Library. So you have 5 sources (one wonder and four specialists). This will give you a 3/5 = 60% chance of getting a great scientist, a 1/5 = 20% chance of getting a great engineer, and a 1/5 = 20% chance of getting a great artist.

* You have the Pyramids (great engineer source) in a city. One turn before the city reaches the threshold to produce a great person, you hire a scientist. What happens? Well, the game remembers that for every turn but the last, the great engineer source had been the only source of GPPs, and that only on the last turn there had been a different source present. So it is a 100% chance of getting a great engineer during all turns but the last, and a 50%/50% chance for the last turn. Since it averages the odds over all the turns, you will have a 99% chance of getting a great engineer, and a 1% chance of getting a great scientist.

* Assuming normal game speed, no great person generated yet: You hire a priest specialist for 22 turns. Then you fire him, and hire two scientist specialists for 11 turns. Intuitively, one would assume that because you had 22*1=22 sources for a great prophet and 11*2=22 sources for a great scientist, this would give you a 50%/50% chance. But because the game averages over turns, the odds will be 22/33 = 67% for a great prophet and 11/33=33% for a great scientist instead, because you had 22 turns with only great prophet sources and 11 turns with only great scientist sources.
(Thanks to Roland Johansen for suggesting this!)

Once the threshold is reached and a great person is generated, the city "forgets" which types of sources there had been before and starts anew. So if you hire a scientist to produce a great scientist, and after generating that great scientist remove the scientist specialist and hire a priest instead, you will have a 100% chance of getting a great prophet as the next great person, since the city will have forgotten that there had been a great scientist source in the city during the previous cycle.

If you have comments, questions, or found any mistakes, feel free to comment!

-Kylearan

2. ### RequiesPrince

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Nice to know, especially the odds of getting a GP. I always wondered why my Prophet cities had so high of a percentage on Engineers or Scientists .

Req

3. ### LittlewolfChieftain

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Excellent post. It is great to summarize a long evolving thread into one post which displays all the conclusions and rules in one place for one topic, such as great people generation. Hopefully we will see more summaries like that!

4. ### Roland JohansenDeity

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Very good article, especially the bit about the chances to get a specific type of great person is interesting. But I still have a question about it:

Assume a city starts producing its next great person:
It starts with 3 turns with 1 priest specialist and ends with one turn of 3 engineer specialists. At that moment the great person is born (ok, this city needs some very large percentage bonus to great person production, but it is only a simple example).

According to your article, we would have 3 turns with a 100% great prophet production and 1 turn of 100% great engineer production which results in a 75% chance for a great prophet and a 25% chance for a great engineer.

Intuitively, I would expect the game to produce a great prophet with 50% chance and a great engineer with 50% chance because 3 of the 6 great person sources were priests and 3 of the 6 were engineers. But what you're saying is that it works differently and that the results of the turns of great person production are important. Do I understand this correctly?

5. ### Kylearancompound eye

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Hi,

Thanks!

Yes, that's indeed the case. I've just set up a "real life" test: 22 turns with a priest and 11 turns with two scientists resulted in roughly 67% chance for great prophet and 33% chance for great scientist.

I'll add that in tomorrow; thanks for suggesting this!

-Kylearan

6. ### Roland JohansenDeity

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Wow, thank you for testing this so quickly. It's good to know how this works exactly!

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Nice article, I never new the exact formula for odds before. Roland Johansen's example clearly shows that.

8. ### karminaWarlord

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ARGH! What an annoying bug. Can we be sure these are indeed the actual chances or only the values displayed the turn before the GP is born? Many players have reported that tiny chances for certain GPs too often lead to this GP getting born.

I really wish GPPs were counted individually for each type! All this random stuff is extremely annoying. (Though still much better than Civ3, admittedly )

9. ### Kylearancompound eye

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Hi,

I'm not sure this is a bug but a design feature. Averaging the odds over turns or over sources is equally valid, and they had decided to go for turns.

We can't really be sure about that, but I highly doubt the programmers used different routines for calculating the displayed odds and calculating the odds when actually determining which great person to generate. It's much easier and straightforward to use the same routine for that, so I think the displayed odds are correct.

I chalk that up to selective attention. If you get the great person who had the greatest odds, you won't notice it. But if you really want the engineer which had a 95% chance of being generated, and got that artist instead, it will grab your attention much more.

Maybe, but it also opens up yet another strategical layer - do I really want to mix different types in one city? Or will I risk trying to build a wonder in a city with lower production instead, to keep only one source of GPPs in my high-production city?

I like it. YMMV, of course.

-Kylearan

10. ### slothmanEmperor

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So every turn it adds one point of chance if at least 1 GPP of that type is added?
20 Scientists will add one point of chance while 2 will also.
The number of total points only determines when.

So if you have 33 turns of 2 sci and 22 of 1 pro then a Great scientist will have a 60% while the Prophit will have 40%?
What if you have the Library wonder and a sci specialist versus 2 sci specialist during the 33 turns?

As a more complicated example, what about 1 artist for 10 turns, 1 merchant for 20 turns and 1 scientist for 30?
These of course assume that the required total GPP's are exactly what is added, to make it easy.

11. ### Kylearancompound eye

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Hi,

For every individual turn, it adds 'one point of chance' for every source of GPPs. So in your example, 20 scientists will add 20 points of chance, and 2 scientists 2 points. But because the odds are averaged over all turns, in the end it will be like your example, because you only had one type of source present each turn.

That's correct. #GPPs = when, #sources = what. (Maybe I should edit this into the article)

Correct.

The Great Library grants you two free specialists which act as GPP sources too, so that's a bit more complicated. But if we ignore this for now, then the odds are the same whether you have a wonder and a specialist, or two specialists.

10/60=17% great artist, 20/60=33% great merchant, 30/60=50% great scientist.

-Kylearan

12. ### PragmaticPrince

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So what you're saying is, if we want to be sure of getting at least SOME of our individualized great people, we've got to have cities with roughly equivalent GPP production (so they rotate: as each gets its great person, it falls to the end of the line), each with its own "wonder" emphasis?

And toss the extras in different cities (e.g., all the extra prophet wonders, and the occasional national wonder)? And still expect to get more prophets, because of all the prophet wonders and the multiple sources of priest specialists?

Hmmm... I got some planning to do...

13. ### Kylearancompound eye

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Hi,

Did I say this?

Anyway, whether it's better to concentrate your GPP production in one city, for the cost of maybe getting a 'wrong' type of great person, or dedicate several cities to different types of great persons for the cost of raw GPP production, is yet another trade-off choice Civ 4 has to offer. See also Vol's article on this subject mentioned in my first post.

-Kylearan

14. ### HeroesHeroes of Might and Magic

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Great article! Since number of source is so important in determing type of GP, and great engineer is the most useful one (not many people will object, I guess), it makes a lot of sense to build all the engineer source wonders in a city: pyramid, hanging garden, hagia sophia (its own effect is just so so, but for GE ...), pentagon, ... Any other?

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You've build the pyramids, giving you 2 points towards great engineer.
But it will take 50 turns to get one that way.

After 20 turns, using caste system and running a food deficit you hire 6 specialist merchants, for three turns. You grab the money from the merchant specialists, finish the great person not in 50 but in 23 turns and still have a 92 % chance of getting a great engineer.

16. ### LeSphinxBachogwa

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Yes Radbad, I will try to built Pyramids more often in order to generate sooner a Great Enginner very usefull in order to rush an important wonder!
LeSphinx

17. ### PragmaticPrince

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Sorry. By "so you're saying," I meant, "so your article implies to me."

Is it just me, or are Scientist GPP sorely lacking? I don't have my manual in front of me (at work on coffee break), but I seem to recall only the Great Library (WW) and the Oxford University (nw) give direct scientist GPP, while there are several that let you turn people into scientists.

And I just like spreading the WWs around, since you can't dump all the nw into one city. It helps to specialize a bit: a GP farm (national epic & globe theater, focused on food/growth and some production, and the increased GPP world wonder (?)), a primary military city (heroic epic & west point, focused on production, sited on a coast), a supporting military city (ironworks & red cross, focused on production, sited on a coast), a commerce city (wall street & oxford university, sited on a coast, acting as holy city to one or more religions, focused on commerce), plus one city for each great person, with roughly balanced GPP production (meaning needs the world wonders and enough food for a few specialists).

Anyway, break's over.

18. ### KrikkitTwoImmortal

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Space Elevator, Red Cross, and Scotland yard also are Great Scientist making wonders (and I think Oxford and the GL are the only ones that give/allow Scientist specialists though)

19. ### RequiesPrince

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The Red Cross and Scotland Yard also are a Scientist source (you can check out my Buildings File for a complete listing according to type of GPP and other goodies), but since you get them so late, they don't help that much.

Heh, I have similar city ideas.

Req

20. ### RequiesPrince

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Hmmm, oops, looks like I had the Space Elevator mislabeled as Great Engineer .

Thanks for the update, Krikkitone!

Req