You've just watched £30,000 land in your current account — an inheritance, a redundancy payout, the sale of a flat you inherited from a relative you barely knew — and now every finance forum you've ever scrolled past suddenly has an opinion on what you should do with it. Half the comments tell you to drip it in over twelve months so a crash doesn't wipe you out on day one. The other half call that advice cowardice dressed up as prudence, and both sides argue their case with equal conviction. Only one of them is actually backed by the maths.
The two options, stated plainly
Lump sum investing means putting the entire windfall into the market in one go — buy the index fund, buy the shares, done, on day one. Drip-feeding, sometimes called pound-cost averaging, means splitting that £30,000 into instalments — say twelve monthly chunks of £2,500 — and feeding it into the market gradually while the rest sits in cash earning very little. The appeal of drip-feeding is obvious: if the market drops 15% in month two, you've only got a fraction of your money exposed to that fall, and the next instalment buys in cheaper.
That logic isn't wrong. It's just incomplete, and the part it leaves out is the part that decides the outcome most of the time.
What the historical data actually shows
Vanguard has run this exact comparison using historical market data from the UK and the US stretching back decades, and the finding holds across both markets: investing the full lump sum immediately beat drip-feeding it in over the following twelve months in roughly two-thirds of the periods tested. The reason isn't complicated once you sit with it. Markets rise more often than they fall — the FTSE All-Share and the S&P 500 have both spent the overwhelming majority of calendar years in positive territory — so money sitting in cash while you drip-feed it in is money that's out of the market during the years it was more likely to go up than down. Drip-feeding is, structurally, a bet that the next twelve months look like 2008 or early 2020. Most twelve-month periods don't.
None of that means drip-feeding is a bad strategy in absolute terms — it means it's a strategy optimised for a specific outcome, a near-term crash, at the cost of underperforming in every other outcome, and crashes are the minority case, not the majority one. If you'd drip-fed £30,000 into a FTSE All-Share tracker across the twelve months following March 2020, you'd have missed a chunk of one of the sharpest rallies in the index's history, because most of your money was still sitting on the sidelines while the market clawed back its losses. Timing luck cuts both ways, and betting on the unlucky side isn't a neutral choice.
Why most men get the maths wrong here
Take the lump sum. That's the better default for most windfalls, and there's no need to dress it up as a softer recommendation than it actually is. If you've already got your emergency fund sorted and you're investing money you won't need for at least five years, spreading it out over a year doesn't reduce your risk — it just reduces your expected return while making you feel better about a risk that was already smaller than you think. Feeling better isn't nothing, but it isn't free either, and you should know the price before you pay it.
The behavioural catch nobody puts on the spreadsheet
Here's the part the maths doesn't capture: what happens to you, specifically, if you put £30,000 in on a Tuesday and the market is down 12% by the following month. Some men shrug and hold. Others check their portfolio every morning, spiral, and sell at the bottom — which turns a temporary paper loss into a permanent real one and undermines the entire argument for investing in the first place. If you know, honestly, that you're the second type, the statistically "correct" answer stops being correct for you personally. That's not a hedge. That's just accounting for a real variable the spreadsheet leaves out.
When drip-feeding genuinely earns its place
There are three situations where spreading the money in makes sense rather than just feeling safer.
- You're investing a genuinely large sum relative to your net worth — say a £200,000 inheritance for someone who's never held more than £15,000 before — where the psychological adjustment matters as much as the maths.
- You believe, with a specific and reasoned view rather than a vague unease, that valuations are stretched right now. That's a market call, and you should recognise it as one rather than pretending it's risk management.
- Money you'll need within two or three years has no business in the stock market at all, drip-fed or otherwise — that's a cash or short-dated gilts problem, not an investing-strategy problem.
Outside those cases, and a handful of others worth weighing on their own merits, drip-feeding is mostly a comfort blanket that costs you expected return. Skip the twelve-month schedule unless one of those three genuinely applies to you.
The one legitimate reason to split it that has nothing to do with market timing
There's a genuine, non-superstitious reason to spread a large windfall across more than one go that has nothing to do with predicting a crash: your ISA allowance resets every 6 April, and it currently sits at £20,000 a year. If your windfall lands in, say, February and comes to £35,000, you can't shelter all of it inside an ISA wrapper in one tax year — you'd use this year's £20,000 allowance now and the remaining £15,000 the moment the new tax year opens a few weeks later, keeping the balance in a general investment account or in cash in the meantime rather than leaving it exposed to capital gains tax indefinitely. That's not drip-feeding for risk-management reasons. It's using two tax years' worth of tax-free headroom instead of one, which is a straightforwardly better outcome regardless of what the market does next. Anyone telling you to spread money in for "safety" should be able to explain which of these two reasons — tax wrapper limits or market timing — they actually mean, because only one of them survives scrutiny.
Where the money actually goes matters more than when
Plenty of men who get the lump-sum-versus-drip-feed decision right still undermine themselves on the next one: which fund. There's a strong pull towards the FTSE 100 simply because the names are familiar — Shell, HSBC, BP, the high street banks — but that index is heavily concentrated in energy, mining and financials, and it has lagged badly behind the S&P 500 and broader global indices over the past decade because it's underweight the technology and healthcare growth that drove most of the developed world's returns. Putting the whole windfall into a UK-only tracker because it feels more familiar, or more patriotic, is a real and common mistake — not a hypothetical one. A global tracker such as a FTSE All-World or FTSE Global All Cap fund gives you exposure to the US, Europe, Japan and emerging markets in roughly the proportion the world's economy is actually weighted, and for a single-fund holding that's the sensible starting point for most men, full stop. Home bias feels safe because it's familiar. It isn't the same thing as safe.
The hybrid that actually works
If the all-at-once approach still makes your stomach turn even after reading the data, there's a version that keeps most of the statistical edge while dulling the worst-case regret. Put 70–80% in immediately across a low-cost global tracker — something like Vanguard's FTSE Global All Cap or a comparable HSBC or iShares fund on a platform such as Hargreaves Lansdown, AJ Bell or the cheaper interactive investor — and drip the remainder in over three or four months rather than twelve. You capture most of the upside a full lump sum would have given you, and you buy yourself a genuine, if smaller, hedge against the specific bad luck of investing everything the week before a crash. It's not the mathematically optimal answer. It's the answer a rational man who also has to sleep at night can actually stick with, which matters more than optimality on paper.
Platform costs matter more than most men assume
Whichever route you take, the platform fee you're paying compounds over decades in a way that's easy to underestimate. A 0.45% annual platform charge on £30,000 sounds trivial next to a market move of 12% in a month, but held over twenty years it works out to tens of thousands of pounds in foregone growth — check the current fee tables before you commit, because they change, and the cheapest platform for a £30,000 pot isn't always the cheapest one for a £300,000 pot five years later.
What to actually do with your windfall
Work out your number first — the emergency fund, the short-term commitments, anything you need within three years — and set that aside in cash before you think about investing a penny of the rest. Once that's done, invest the remainder as a lump sum unless you have a specific, honest reason not to, and if you do have that reason, use the 70/30 or 80/20 split over three to four months rather than stretching it needlessly across a full year. Then close the app. The single biggest threat to your returns from here isn't a market crash — it's you, checking the balance every day and letting twelve months of noise talk you out of a decision the data already made for you.