Choose your Optional Subject for UPSC Mains (General Studies) rationally according to your interests since you would have to complete and read the entire syllabus and revise it multiple times for one year. If you have sufficient interest, it becomes easier to sustain the preparation for a year or more than a year if you decide to give it one more go. It is imperative to finish your optional at least 75 %  before the UPSC Preliminary Examination because it will help you to revise the syllabus after Prelims immediately as you get a time of around three months between the preliminary and the Mains Examination for UPSC. You must be aware that during this time, you must revise the four general studies subjects, prepare essay writing and revise the UPSC Mains Optional Syllabus simultaneously.

There are many essential factors to be kept in mind while you decide to select an Optional Subject for UPSC Mains:

The interest of the aspirant in chosen Optional Subject for UPSC:

The predominant factor in deciding on the Mains Optional Subject for UPSC should be primarily your interest in the given subject. The best way to determine is first to complete the fundamentals of the General Studies NCERTs and fundamentals. During this period, you should find out which optional subjects generate interest in you. At the same time, you should review the UPSC Prelims & Mains syllabus, UPSC previous year's question papers on the optional subjects, and basic reading material. Your comfort level in reading and comprehending it will enable you to make a properly informed decision. If the subject interests you, you love reading it, and you are eager to learn more about it, it will enable you to open up your mind and speed up your study of the subject.

Background of the aspirant for UPSC Mains Optional Subject:

Choosing an Optional Subject for UPSC that the candidates have studied during graduation might be beneficial because they have already learned it. They must restructure and organize the information as per the UPSC Syllabus for Mains. Nothing has to be studied from scratch here. This mechanism might be more helpful to candidates with professional education in Engineering, Medical Sciences, or Business administration. This choice may be highly beneficial for students pursuing their education and, simultaneously, wanting to prepare for the civil services; or those who start their UPSC Exam Preparation for IAS while in college. Starting your preparation in college makes you organize your thoughts more clearly, gives you more time for revision, and gets a good grasp of all the fundamentals essential to clear the examination.

Availability of literary resources/ Study material and coaching:

The syllabus of the optional papers is vast, so having quality notes from a good coaching institute and attending the classes either physically or online would tremendously benefit covering the Main Optional syllabus in a short period. The best coaching classes can be found by enquiring from friends, peers, veterans, and who have been selected. The Internet can also be a valuable source in helping you make this decision through YouTube videos and blogs. A candidate can attend coaching classes, but his lack of interest in the subject can render the exercise futile. This methodology is better for candidates who have lost touch with graduation subjects.

Contribution of the Optional Subject to General Studies syllabus/ Overlap with General Studies (GS):

The General Studies Mains Examination syllabus does not require subject specialization, considering this factor in selecting your Optional Subject for UPSC might prove fatal. On the other hand, the Optional subject for the Humanities stream syllabus is of the post-graduation level. The Engineering and Medical streams, it is of the graduation level. Therefore, basing your decision on the overlap of the general studies syllabus is not recommended.

Popularity and the performance of the optional subject for UPSC in the recent past:

There can be Optional Subjects for UPSC that do not fetch the desired marks compared to the effort put in by candidates. This can take the form of a few years of toughness either in the questions asked or the awarded marks. Several UPSC candidates go for an option chosen by most UPSC aspirants. There are multiple reasons for the popularity of these subjects, either having a limited syllabus or high scoring for some candidates or basically because there are more candidates with these subjects as their graduation subject.

Time Management:

Besides interest and comprehension ability, candidates should know how much time they would require to study an Optional Subject. The candidates would have to revise the entire syllabus for their Optional along with the General Studies Main syllabus within three and a half months add as such. There should be ready with their micro notes and follow spaced repetition techniques for systematic revision.

Success rate:

The success rate is the number of candidates recommended as a percentage of those interviewed. Thus, in totality, the success rate of candidates having higher degrees was higher than the candidates having bachelor’s degrees. 922 or 40.1 percent of the candidates interviewed were recommended for appointment to various Civil Services in 2019. Of them, 672 (72.9%) were graduates and 250 (27.1%) possessed post-graduate or higher qualifications.
The Optional Subject-wise distribution of candidates who appeared in the Civil Services (Main) Examination, 2019 and were recommended for an appointment with their success rate is shown below:

Table 1 Distribution of Candidates who Appeared vis-à-vis Recommended by Optional

Serial No	Optional Subjects	Number of Candidates		Success Rate
		Appeared	Recommended
(1)	(2)	(3)	(4)	(5)
1.	Agriculture	124	13	10.5%
2.	Animal Husbandary & Veterinary Science	16	3	18.8%
3.	Anthropology	1189	108	9.1%
4.	Botany	28	2	7.1%
5.	Chemistry	156	13	8.3%
6.	Civil Engineering	146	15	10.3%
7.	Commerce & Accountancy	183	20	10.9%
8.	Economics	243	26	10.7%
9.	Electrical Engineering	200	16	8.0%
10.	Geography	1916	105	5.5%
11.	Geology	30	0	0.0%
12.	History	751	51	6.8%
13.	Law	186	19	10.2%
14.	Management	54	6	11.1%
15.	Mathematics	539	45	8.3%
16.	Mechanical Engineering	213	12	5.6%
17.	Medical Science	247	26	10.5%
18.	Philosophy	439	27	6.2%
19.	Physics	165	12	7.3%
20.	Political Science & International Relations	1662	137	8.2%
21.	Psychology	164	15	9.1%
22.	Public Administration	705	58	8.2%
23.	Sociology	1263	126	10.0%
24.	Statistics	2	0	0.0%
25.	Zoology	44	4	9.1%
26.	Literature of Assamese Language	3	0	0.0%
27.	Literature of Bengali Language	1	0	0.0%
28.	Literature of English Language	31	3	9.7%
29.	Literature of Gujarati Language	85	3	3.5%
30.	Literature of Hindi Language	191	13	6.8%
31.	Literature of Kannada Language	124	17	13.7%
32.	Literature of Maithili Language	53	2	3.8%
33.	Literature of Malayalam Language	53	2	3.8%
34.	Literature of Manipuri Language	7	0	0.0%
35.	Literature of Marathi Language	6	0	0.0%
36.	Literature of Oriya Language	3	0	0.0%
37.	Literature of Punjabi Language	18	1	5.6%
38.	Literature of Sanskrit Language	53	2	3.8%
39.	Literature of Sindhi (Devanagari) Language	2	1	50.0%
40.	Literature of Tamil Language	77	5	6.5%
41.	Literature of Telugu Language	32	1	3.1%
42.	Literature of Urdu Language	18	2	11.1%

The following points emerge from the Table:

1. Geography Optional Subject for UPSC was the most preferred subject among the optional subjects UPSC chosen by the candidates, followed by Political Science & International Relations, and Sociology.
2. Amongst the subjects opted by 100 or more candidates, the highest percentage of successful candidates had opted for Literature of Kannada Language (13.7 percent) followed by Literature of Malayalam Language (12.4 percent) and Commerce & Accountancy (10.9 percent).
3. As far as the academic backgrounds of the recommended candidates are concerned, 63.1% were from Engineering, followed by 24.2%, 6.6%, and 6.1% respectively from Humanities, Science, and Medical Science respectively. 
4. 82.6% of Optional Subjects for UPSC opted by the recommended candidates were related to the Humanities (including the literature of languages), followed by 9.6%, 4.7% and 3.1% respectively related to Science, Engineering, and Medical Science respectively. This shows that most of the candidates have made a cross-domain shift from their original stream (i.e., Engineering and Medical Science) to humanities.