Differential Privacy has its limits for small data sets. Luckily, more research is on the way to run arbitrary calculations on multiple datasets that remain private in its entirety (basically homomorphic encryption, but efficiently) [1]. Algorithms that work reasonably well are simple statistical tests and ridge regression [2].

I think these innovations are rare instances where technology can really solves a social problem.

[1] https://www.microsoft.com/en-us/research/microsoft-researche... [2] https://www.microsoft.com/en-us/research/wp-content/uploads/...