# How to build an adequate SARIMA model?

I'd appreciate some help with my data. I have to find (S)ARIMA models to fit some exportations data, but for some of them, I can't find an easy model by just looking ACF and PACF plots. So I change randomly $p,d,q$ and $P,D,Q$, but some data are really difficult to fit. Here is an example, I spent hours at modifying parameters, and don't find a good model with significant coefficients and good ACF et PACF plots of residuals. Here are pictures of time serie of exportation, and PACF (I could not post ACF because I don't have enough reputation to post more than 2 links, but nothing was significant).

I am super interested if someone could give me a good model, because I feel like I will never find a good one. But I am even more interested in understanding how you find a good model for that kind of complex data. Here are the data. Thanks in advance.

- 22,04761905
- 21,36363636
- 20
- 22
- 19,19047619
- 21,81818182
- 18,68421053
- 22,9047619
- 20,38095238
- 21,27272727
- 20,68181818
- 18,6
- 17,39130435
- 19,86363636
- 18,68421053
- 20,42857143
- 19,1
- 21,2
- 19,19047619
- 21
- 19,8
- 22,52173913
- 19,52380952
- 18,52380952
- 18,7826087
- 21,9047619
- 15,45
- 23,38095238
- 22,05
- 20,57142857
- 19,5
- 18,80952381
- 18,9
- 19,86956522
- 17,55
- 18,18181818
- 22,69565217
- 19,5
- 19,23809524

• what did you think? – Tom Reilly Apr 7 '16 at 20:31
• nice work ! residuals from your model are approximately random ...thus u r good to go ! – IrishStat May 27 '19 at 17:15