My book at bedtime this week has been a history of buy-to-let. The Association of Rental Lettings Agencies (Arla), which invented the concept, has published an archive of statistics, garnered during the past seven years from 500 of its 1,800 members and 200 landlords.

About a quarter of the respondents came from prime central London, half from the southeast and the remainder from the rest of the UK. The resulting information has all been crunched into a number of tables to form an eight-page handbook.

And, without wishing to sound like a total property bore, it makes an interesting read. One table, for example, reveals that, during the past five years, you would have been better off with a buy-to-let flat (average annual yield of 5.1%-5.6%) than a house (4.9%-5.4%). Another table reveals that the average age of a landlord is 46½. And the following one reveals that the average landlord has been doing it for 6½ years.

Contrary to expectations, tenants in London are inclined to stay where they are for almost three months longer than their regional counterparts. Also, at the moment, more landlords are buying (30%) than selling (15%), thus torpedoing the prevailing notion that they are flogging everything in a panic.

Background

• Tales of a landlady: Tax reforms

• Into the sunset

Background

• Tales of a landlady: Degrees of success

• Tales of a landlady: It pays to shop around

• Tales of a landlady: Residents only

• The ties that bind

• How low can you go?

Background

• Tales of a landlady: Avoiding the agents

• Tales of a landlady: In the dock

• Tales of a landlady: the age of reason

• Tales of a landlady: Heroes and villains

• Tales of a landlady: High maintenance

Background

• Back to the ’burbs

• A waste of energy?

• Tenants like gardens, but not tending them

• In the doghouse

• Parking mad

It’s eviction time

Can investors profit from the rise in repossessions?

• It’s eviction time

Background

• Do property workshops work?

• A letting gamble

• Spread betting

• When buy-to-let turns from a hobby into a living

Tales of a landlady: Persistent complaint

How can lettings agents justify annual renewal fees, asks Rosie Millard

Background

• Landlords: halo or horns?

• Bidding wars

• Time to quit the ring?

How useful is all this? Has Arla merely spent a lot of time compiling statistics with which I anticipate wowing people at dinner parties?

“I would say that statistics like this are all relevant,” says James Agace, a landlord with a portfolio of 50 serviced flats in central London (and who, by the way, is 39). “I think knowing the average age of landlords is interesting. It’s a reasonably young age, and shows the dynamism in the sector.”

A strange rustling sound comes down the line. Agace tells me that he is pacing around the gravel drive of his six-bedroom home in Surrey. (Owning 50 flats has obviously been good for his bank balance.) Still, he thirsts for information. “There are few statistics on buy-to-let out there,” he says. “Reading that 86% of landlords would not sell their properties, even if there was a price crash, was fascinating. And typical – landlords never want to acknowledge that they have paid too much. You like to see what’s going on, but you have to know that the London market is a bit of a bubble. And that, frankly, outside the capital, it’s not all that rosy.”

Yes, but if you aren’t actually going to pour your money into Liverpool, or Hull, or Leeds, then knowing that things are tricky in property investment in those places is useful only in the way that being smug is useful.

“How can a national survey help the individual landlord?” asks Barry Markham, 51 (since you ask), the chairman of the National Federation of Residential Landlords. He has yet to read the Arla publication. That speaks volumes – particularly because it’s not voluminous.

Markham, who has a portfolio of about 50 flats and houses in Hastings, East Sussex, is clearly someone who focuses wholly on the local variations in the market, because that is where he has ploughed all his money. Yet maybe the Arla history is useful, I counter, as an indicator for finance lenders. If you were armed with the knowledge that, on average, voids have gone down from 4.4 weeks a year in 2003 to 3.6 in 2007, that might be useful in conversation with the bank. Maybe.

“Hmm,” says Markham. “I would not base my buying or selling on this or any other national survey, because buy-to-let is regionally sensitive. And there are so many different markets, depending on whether you are renting out to tenants on benefits, students or City professionals.”

What does he use for confidence-boosting information, then? Don’t tell me his portfolio has been acquired via a leap of faith. Well, actually, yes. “It is a leap of faith,” he says. “But you must get local information and chat to other landlords and letting agents. That’s much better than a national survey.”

John Heron is the director of mortgages at Paragon, one of the biggest buy-to-let lenders in the UK. As far as he is concerned, Arla’s slim volume is essential reading. “We have moaned and groaned about the paucity of general information on landlords,” he says. “When we offered our first buy-to-let loan, nobody knew what a landlord was. This history is useful because it tells you a number of things about the quality of the market. Yields, for example. And voids. It makes decisions from lenders or borrowers much better informed. The more data landlords have – about things such as tenant demand, for instance – the more likely they are to be successful.”

So, let us quickly cross to another table, showing that 42% of respondents think there are more tenants than properties out there, and in London in particular. “That’s been particularly missed in the whole emotive ‘first-time buyer against evil landlord’ debate,” Heron says. “The issue is not first-time buyers but the fact that there are loads of tenants out there, with a shortage of properties.”

Download The ARLA History of Buy to Let Investment 2001-2007 from www.arla.co.uk

buytolet@sunday-times.co.uk

Times recommends

• Analysis: frustration for everyone - except investors
• Buy-to-let: professional investors cash in on the credit crunch
• Ten things you need to know about house prices