I’ve just made a huge decision about my Scottish Mortgage shares!

Investors have remained incredibly loyal to Scottish Mortgage Investment Trust (LSE: SMT), despite a bumpy few years.

Many doubtless remember its halcyon days, when the FTSE 100-listed tech-focused trust returned more than 500% in five years, and are clinging on for hopes of a repeat.

The Scottish Mortgage share price crashed by more than 50% in 2022. That was a terrible year for tech but the trust fell far harder than the tech-heavy Nasdaq index, which ended the year down ‘just’ 28.39%.

Is it all it’s cracked up to be?

I took advantage of the crash to buy Scottish Mortgage shares in May and August last year. So far, I’m up 21.83%. Measured over 12 months, the shares are up 25.83%. That’s respectable, but on reflection, not great.

Scottish Mortgage typically holds between 50 and 100 investments, many privately held companies. The advantage of targeting the volatile disruptive tech sector through a trust is that is spreads risk. The downside is that investors will never get the sheer joy of holding a big winner like Nvidia.

The chipmaker is the trust’s single biggest holding at 6.79% of the portfolio, up almost 200% over 12 months. Scottish Mortgage investors have exposure but aren’t really sharing in the fun. They’ve also been exposed to the misery of holding non-listed Swedish battery maker Northvolt, now in meltdown.

That’s why I only buy individual UK stocks these days, never funds. I’d rather make my own winning and losing bets.

I do buy funds covering overseas markets, but mostly trackers. I’ve just realised that Scottish Mortgage is now the only actively managed fund I still hold. Can it justify itself to me?

Manager Tom Slater has done reasonably well out of the US stock market bull run, but not brilliantly. The S&P 500 is at a record high after climbing 34.37% over the last 12 months. Scottish Mortgage is trailing by some distance.

The stock is underperforming

The Nasdaq is up 45.07% over the last 12 months. This means Scottish Mortgage fell at almost twice the speed during the 2022 crash, but rose at roughly half the pace in the recent boom. That’s not good enough.

I hold shares in the Legal & General Global Technology Index Trust, which covers the same territory. It’s up 37.69% over the last year. Again, Scottish Mortgage is lagging badly.

Many are anxious about the outlook for tech and the US. Consultancy Longview Economics has warned the next few months could be bumpy as the Federal Reserve struggles to deliver a soft landing and a knife-edge presidential election looms.

It suggests that “this bull run is due a major setback”. If it’s right, Scottish Mortgage will doubtless suffer a major setback too, but that’s not my concern.

I don’t sell shares every time somebody warns of a crash. Timing the market rarely ever works. Instead I buy and hold for the long run.

But I’m finding it hard to justify holding on to this one, given its underperformance in both bullish and bearish market conditions. I think now may be the right time to take my modest profit and sell.