Non-halachic Reform Jews are those whose mother was not Jewish, yet they consider themselves Jewish because of either a heterodox conversion or patrilineal descent. We can mostly figure out the demographics from particular questions asked in certain surveys.

According to the [2013 Pew Study][1] on American Jews, **10%** of American adults who identify their religion as Judaism and their denomination as Reform say that their mother was not Jewish. (19% if you include those who consider themselves Jewish "aside from religion" and Reform, but we're going to focus on those who consider themselves associated with Judaism in some form.) Assuming that the percent of these people who converted Orthodox and later changed to Reform is negligible (which seems to be backed up by the data), we can assume that practically all of these individuals are not halachically Jewish.

This gets more complicated when we consider the descendants of the female portion of that group. Any of the children who still consider themselves Reform Jews would say that they _do_ have a Jewish mother, and the same for _their_ descendants on the female line. How many people are there in this group?

At the time of the survey, Reform Jewish women who say that their mother was not Jewish were 7.8% of the American (adult) Reform Jewish population. (Yes, the gender balance is massively skewed.) We have a fairly small sample size to work with for this group (less than 60 people), but we can get estimates of some basic points: 85% of the portion of the group with children have Jewish spouses or partners according to the respondent (38% are married to Jewish spouses overall), they have 0.8 children on average, ~1/3 of which are currently minors living in the respondents' homes, most of which are being "raised Jewish". About 55% of people raised Reform Jewish (regardless of whether they say their mother was Jewish) continue to identify as such as adults. Pew did not ask about the current religious affiliation of the respondents' adult children who don't live with their parents, so we'll have to rely on some educated guesses based off of what we know of Reform Jews in general.

So, how many adult Reform Jews have mothers who self-identify as Reform Jewish but are not halachically Jewish? Without taking into account the considerable denominational switching between groups, the amount of Reform converts who were raised not Jewish by non-halachic Reform Jewish mothers but later started to identify with Judaism (Pew only asked those with no Jewish parents whether they had converted), or the differences in norms between generations, or the fact that many of the relevant mothers might be no longer alive, the group might be about **2-3%** of American Reform Jewry. There may also be a smaller group of third-generation descendants of these groups, but probably not enough to make a difference.

So, approximately **87%** of adult Reform Jews in the United States are halachically Jewish.

In Israel, according to the [2015 Pew report][2] on the country, 3% of the Jewish population identifies as Reform. According to the report, **100%** of the 89 Reform respondents said that their mother was Jewish.


  [1]: http://www.pewforum.org/2013/10/01/jewish-american-beliefs-attitudes-culture-survey/
  [2]: http://www.pewforum.org/2016/03/08/israels-religiously-divided-society/