Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Thoughts on new statistical procedures for age-period-cohort analyses   Age-period-cohort analysis is mathematically intractable because of
fundamental nonidentifiability of linear trends. However, some understanding
can be gained in the context of individual problems.

0
The categories of this paper are: hep-ph
32
The categories of this paper are: atom-ph
7
The categories of this paper are: hep-th
15
The categories of this paper are: nucl-ex
35
The categories of this paper are: mtrl-th
33
The categories of this paper are: plasm-ph
37
The categories of this paper are: supr-con
8
The categories of this paper are: hep-ex
5
The categories of this paper are: gr-qc
4
The categories of this paper are: cond-mat
19
The categories of this paper are: eess
11
The categories of this paper are: hep-lat
34
The categories of this paper are: chem-ph
27
The categories of this paper are: comp-gas
3
The categories of this paper are: physics
36
The categories of this paper are: cmp-lg