Does fund manager tenure length matter?

Just as Joe Biden was inaugurated I received an interesting note from Interactive Investor. The email used the hook of Joe Biden being the oldest US President in history as a reason to look at the longest-serving fund managers out there and how they have outperformed the market.

The research piece stated:

Fund managers that have racked up the longest track records are likely to have done so in large part because good performance has kept them there.... it is interesting to see that eight out of ten of the longest serving open ended fund managers have outperformed their benchmark during their tenure (or as far back as comparable records will go).

It also contained the following chart detailing the outperformance of the fund managers in question over time (you can scroll right on the chart to see more data):

Unit trusts star managers Manager Fund name Manager Tenure (years) Effective Performance from Return Benchmark Benchmark return Andy Brough Schroder Institutional UK Smaller Companies 33 08/06/1987 14/09/1999 775.70% FTSE Small Cap Ex Invest Trust TR GBP 213.8%* Sue Round EdenTree Amity UK 33 01/03/1988 01/03/1998 1144.60% FTSE AllSh TR GBP 1,244.6%* Geoff Hitchin Marlborough Global Bond 33 05/08/1987 01/02/1990 1009.10% BbgBarc Global Aggregate TR USD 596.0%* Alistair Whyte Aberforth UK Small Companies 30 29/03/1991 29/03/1991 2639.30% Numis SC Ex Invt Com TR GBP 1519.50% Robin Hepworth EdenTree Higher Income 26 17/11/1994 09/12/1999 388.60% FTSE AllSh TR GBP 140.5%* Makiko Hakozaki Russell Inv Japan Equity 25 30/06/1995 30/06/1995 219.60% TOPIX TR 115.50% Justin Abercrombie Schroder QEP US Core 25 19/02/1996 19/02/1996 523.60% S&P 500 TR 951.70% Daniel J.