As an insurance agent, I can tell you there are certain factors that play into your rates.
1) Age - under 25 and over 70 your rates are at their highest
2) Credit - poor credit causes rates to be higher. Typically, if someone has poor credit, they do not pay their bills on time and are more likely to lapse in coverage. Statistically, they are involved in accidents more, file a claim more often and receive citations more frequently.
3) Area - your zip code will affect your rates. Certain areas have a higher claim ratio than others, so even if you have a perfect record and good credit, you get "penalized" for the poor drivers
4) Relationship status - being married gives a lower rate. Married drivers tend to be more responsible when driving, statistically
5) Resident status - Homeowners get a discount, even if the auto carrier doesn't provide homeowners insurance. They tend to be "safer" while driving, statistically.
6) Current/previous liability limits - If you carry the state minimum limits, you are paying more dollar-for-dollar in coverage. If you are shopping around and have the state minimum limits, you are not a prime customer for the other carriers. Statistically speaking, people with the lowest limits file more claims, are involved in accidents more frequently and receive citations more frequently.
7) Previous carrier rating - There are "standard" and "non-standard" companies. If you have a non-standard company, many carriers will pass on you by giving a higher premium. Non-standard carriers typically take drivers that nobody else wants due to tickets, claims, accidents, credit etc
I always recommend my clients to carry what they can afford. When someone complains about say $75/month and they bring in their Iphone 7, Ipad, Starbucks and are decked out, I just think to myself "really?"
I have a 2015 Nissan SUV and a 2008 Jeep and pay roughly $125/month. I carry the highest limits available, so if I were to lower the liability limits, I'd actually be paying more. Sometimes it's worth paying a little more for the first 6 months to carry more coverage, and then shop it afterwards and save money. I do this a lot with my clients who bring in lower limits, they carry higher for 6 months, pay a little more, then we rewrite it at renewal and save them money from where they were before they came to me