Every few years, we update our comparison across Legislatures of the percent of freshmen at the beginning of each regular session. Here's our first post from 2012 on the topic (which explains some of the reasons for unusually high numbers), and the 2014 and 2017 updates.
Below you can see how the numbers compared over the past 50 years, from 1969-2019 (61st-86th Legislatures). Please note that we defined freshmen as new legislators sworn in during the first day or week of the regular session. Members who first served during a called session of a legislature are counted as freshmen members of that legislature. Excluded are members who were elected to a legislature but never sworn in due to death, resignation, or other factors.
You can see these and other figures on our member statistics page. Exact percentage of freshmen each session can be found here.
Data compiled from the library's Texas Legislators: Past and Present database