A certain percentage of the Conservative and Reform Jews identified in the study are not halachically Jewish, either because they’re patrilineal Jews or because they consider themselves Jewish through an invalid conversion of their mother or maternal grandmother. The survey researchers could have asked about whether their mother is Jewish and whether she converted, but as far as I can tell they didn’t. It would be nice to know what percentage of each movement, and what percentage of non-affiliated self-identified Jews, aren’t Jewish at all under Jewish law.
The sample of Orthodox Jews, and especially MO Jews, is very small, and because of this small sample size it’s hard to know whether the results are valid.
There are some oddities in the results that suggest the sampling was inadequate. A pretty large percentage of self-described Orthodox Jews (including ultra-orthodox) indicated that they didn’t refrain from handling money on Shabbos.
The survey found that only 50% of those raised Orthodox were still Orthodox, which contradicts the idea that the Orthodox are so good at retention. However, the numbers are much higher for the younger Orthodox groups, and these numbers are only good if the sample was truly representative. I have a feeling that the more frum families, especially chassidim and those with many children, refused to participate in the study when contacted, because they were too busy or just not interested.
The 1% and 4% kiruv numbers might be correct, but they might underestimate rates of making teshuvah, if a significant amount of BTs make aliyah or if the survey for whatever reason ended up undersampling BTs. Even so, given the anti-Orthodox attitude of Reform and Conservative Jews, and the anti-religious cultural context in which we live at this time, these numbers are not insignificant. They mean there are thousands of new observant Jews, marrying other Jews and raising observant Jewish children.