I remember Jim’s relentless optimism. He clearly saw humanities progress through the lens of demographics where others were worried about «population bombs». He imbued the dry empiricism of demography with hope. I am less optimistic than Jim, but I learned from him to «optimism-check» myself. Demography is known for gloomy projections and there’s never a lack of reasons to assume a turn for worse, but empirically, looking back, optimism made for better demographic forecasts.

Jim was a generous supervisor and gave me the freedom to find my own path. Talking with him, I always walked away inspired. When he learned about my wife’s cancer (all good now) he told me to care for her and that work can wait. He held strong opinions, but invited disagreement.

I’m only realizing now how Jim impacted me, without intense supervision. Closely I read Vaupel (1979), Vaupel-Yashin (1985) and Vaupel-Zhang (2010), ensuring I understood every equation and in turn understanding how he used math to formalize intuition.

Like with all great scientists his ideas will resonate through the generations via those influenced by him.