**Author:** Fridmund K. Shunsaku

Hi,

I have went on to modify the Aiyagari model to include an endogenous labour choice,

following a utility function that is log© + eta log(leisure) , leisure = 1-L

Using the coleman operator, there seem to be a bound for eta, i.e. not all eta has a solution.

specifically any eta greater than 0.1 gives me the error:

```
ValueError: f(a) and f(b) must have different signs
```

is that suppose to be the case (that only some values of eta converges) or have I made a mistake?

The method, follows first searching a range 0 to max a’ and then for each a’,

search for the optimal labour (L) between a range 0 to 1.

(a scipy brentq searching for the optimal L nested in the main scipy brentq)

Generally speaking:

for each i in {0,…, z*L+R*a}

find optimal L between [0,1]

If there is a bound on eta, is there a way (hint/web link/reference) to calculate it / proof that it exists?

Or have I made an error in the code and theoretically any value of eta should actually work?

P.S

I also noticed that changing the grid maximum also changes the maximum value of eta.

And have tried a different utility specification but they all have some kind of a limit on eta

log( c**eta * leisure**(1-eta) )