Is there any way to boost the Russian Empire's pre-WW1 population without land expansion?

[Israel_Dan the Man]

Whatifalthist has a great video on this, What if the Soviet Union never existed. I recommend you watch.

I was talking about before WW1 but I will check out the video because I really like the guy's videos. My favorites are what if the French won the WoSS (well, won more than they did IOTL) and what if the Holy Roman Empire was a centralized powerhouse with a lot of colonies.