Wednesday, 23 July 2014

A nation of tea-drinkers

For years, the United Kingdom has been known as a nation of tea-drinkers.  Selling tea and tea-bags is a big business, estimated at half a billion pounds per year.  Until the invention of teabags, tea was made with leaves in a pot.  Teapots were to be found in every household, in all shapes and sizes, and associated with the serving of tea came tea-caddies, tea strainers, tea-cups and so on.  Tea-bags changed some of these habits.  With a tea-bag, a cup of tea can be mad by pouring boiling water onto the bag in a cup or mug, so dispensing with the need for a teapot.  For the company making tea, tea-bags mean that finer leaves can be used.  In our household, we use both leaf tea and tea-bags, but almost always use one of our teapots.  (We have four teapots: one holds enough for two cups, the next holds enough for four or five, the third is slightly larger, and my heirloom Victorian one holds ten or so cups.)

Today several newspapers have reported a story about measurement of tea made with tea-bags, to settle a dispute about "What is better?"  And of course, OR is all about "What is better?"  The story can be read here.  It all followed from an advertisement which included this picture:

(c) Daily Mail
The tea on the left is made with a pyramid-shaped tea-bag, that on the right with a round bag.  The claim is that pyramids are better.  A leading manufacturer of round tea-bags claimed that this was a misleading claim in an advert, so there have been laboratory tests whose results are supporting the claims for the pyramids.  Ultimately, it will be up to the consumer, who will apply an OR technique, cost-benefit analysis.  Is it worth buying more expensive tea-bags or not?  But it is nice to see that in the nation of tea-drinkers, people are prepared to study whether one "cuppa" is better than another.

Monday, 14 July 2014

Operational Research Scientists, Architects, Town Planners and Democracy

A couple of years ago, I wrote a blog "I am not an architect" following an editorial in the UK OR Newsletter by the OR Society's then president, drawing parallels between the profession of OR and the profession of architecture.  I was not convinced by those parallels, for a number of reasons.

Recently, I have changed my mind - but not much.  A review led me to the book "Happy City" by Charles Montgomery (CM), which looks at the effect of urban design on the general well-being of the people who live and work in towns and cities across the world.  CM is a passionate writer urging his readers to consider the built environment of their homes and offices.  He draws together strands from many disciplines in his proposals; health, safety on the roads, transport links, general well-being such as knowing ones neighbours, the design of houses and schools and offices.  One chapter is titled "Everything is Connected to Everything Else", and it argues that our towns and cities are complex systems, where changes in one part of the system affect many other parts.  So, building a shop with its own car park affects the number of people who use cars in the vicinity, which changes the safety of the roads there, and influences the use of other forms of transport.

Within OR, recognising that our work affects a system is a general principle.  Because it is not possible to model an entire system, we simplify, but remain aware of the wider ramifications of what we do.  One of the reasons that I took issue with the parallel with the profession of architecture was that the public face of architecture is such that the effect on a wider system is ignored or minimised.

Most of the examples in the book come from outside the UK; CM is from Vancouver in Canada, and writes about that city and others in Canada and the USA, though he has travelled widely in South America, Europe and South Africa.  But it is easy to see how his experiences and ideas can be paralleled in the UK. 

By the time that I had finished the book (it is a long one) I was convinced that the best architects could work to reflect beneficially on the system where their projects were being planned and built.  In so doing, they would move on from being architects to town planners.  (So I am prepared to be associated with the most visionary architects who do look at the system as a whole.)  And then, CM argues, they come across the blockage known as democracy.  Towns and cities are democratic organisations - up to a point.  City officials have rules to follow, some of which are sensible, and some of which have never been examined to see if they are appropriate in the 21st century.  So, CM says, there are constraints (another OR term) on what can be done to an urban system to make it better.  Some of those constraints shackle the town planner.  In other cases, those with power and influence and money can dictate what happens.  Throughout, there are many conflicting objectives - another OR term.

CM argues that urban development is inevitable;  but if the people who control it make sensible decisions about the whole system, with models drawn from transport, health and well-being, and even the concept of measured happiness, then that development will  lead to better places for citizens to live and work.

And what about my home city?  Part of my immediate neighbourhood is purely residential, because the land was sold for housing a hundred years ago, with restrictions that no building be used for trade.  So there are no shops, no offices, no workshops.  And as a result, there are gaps in the system.  To shop, most people get into their cars (OK, I walk or cycle when I can).  To go to work, people move out of the neighbourhood, as there are few jobs here (schools, care homes) and then major employers on the fringe of the area drawing in people from a wide radius.  The road layout was laid out in the 19th and early 20th centuries, and is not ideal for today's mix of road vehicles, pedestrians and cyclists.  We have neighbours who we never see except through their car windows, because that is the only way that they can access work, leisure facilities, commerce.  And the economy of the houses in the area is being forced by the taxation involved on moving home, so it is easier and cheaper to extend or remodel one's home than to move.  Hence there are fewer newcomers to the area, and the social mix is changing - larger, extended houses, are only affordable by the affluent.

Oh dear, Charles Montgomery has convinced me - the urban system is not optimal - it can be improved!

Monday, 7 July 2014

What makes the best blog?

Several free magazines target the residents of Exeter.  To be free, they must draw an income from advertising, so the ratio of articles to advertisements reflects this.   The magazines vary in their mode of distribution; some are delivered with other advertising literature through the letterbox.  Others can be picked up at "select" locations.

We were in one of the latter locations the other day, and picked up the two latest copies of the glossiest free magazines.  Both featured a set of pictures about a meeting for bloggers.  One described it as being a party for the "hundred best bloggers in Exeter", the other was a little vaguer, and said that it was for "a hundred of the best bloggers in the south-west".  Now you can imagine that I was piqued at not being invited(!)

So what makes the best bloggers in Exeter/south-west England? How do you measure the multiple criteria?  What surrogate measures do you use since "best" is not well-defined?

There wasn't much detail with the pictures, but both Philippa and Tina looked at the pictures with me, and remarked that I obviously didn't fit the criteria.  All those pictured were female and nearly all were clearly under 30.  Little was said about the subjects of the blogs, but we read that the party included styling by a local salon, manicures and makeovers, and several of the pictures showed the logo of a major producer of beauty products for women.  (and don't forget the cocktails!) 

Curious, I went to the website, so now I can reveal that to have made it to be one of the hundred best bloggers in Exeter, you needed to book and pay for the meeting, knowing that it was intended for a young, fashion-oriented, female audience.

So that is how to assess the multi-criteria measure of best, when it comes to blogging!  A very interesting way of making the measurements of "best".

I shall continue to write blogs as a non-young, non-fashion-oriented, non-female writer.

What makes a good Operational Research scientist?

Like many readers of the INFORMS journal ORMS Today, I turn to Doug Samuelson's ORacle articles with interest each issue.  In the current issue (Volume 41, number 3, page 56, June 2014) Doug has a quote that resonated with me.  Given a group of "social or industrial psychologists, or something like that" who had irked the hero of his article, that hero said "no matter what degrees those people have and what positions they hold, they're not scientists and they never will be.  The essential quality of a scientist is playful curiosity, and they don't even recognise that quality when they see it".

Sir Hermann Bondi was linked to the O.R. Society in the U.K. for many years.  He once wrote: "Little children, up to the age of five or six or seven, are constantly asking questions starting 'Why?'  Education aims to stop such questions.  But education has its failures.  The results are called scientists."

Perhaps, when recruiting O.R. scientists, we should ask if they have a playful curiosity, or when they last asked a question that started 'Why?'

Check-out mathematics

My dinner-party explanation of operational research has come back to haunt me.

When asked what O.R. can do, I talk about models of the supermarket check-out queue, and ensuring that there are enough check-outs open.  I say "the answer is a number, so there is mathematics involved".

The current issue of the US journal/magazine ORMS Today (June 2014, volume 41, number 3, page 17) has a cutting from Information Week about queues at Kroger shops.  The OR people there have taken the problem one stage further than simply collecting statistics about past queues.  Instead, they have a real-time modelling process which monitors arrivals at the shop door, uses the results of a simulation model to predict the demand for check-outs as a result of those arrivals and their shopping habits, and allocates staff to these.  There are other inputs into the model from the point-of-sale terminals.  One measure of interest is associated with customers not finding a check-out with more than one person ahead of them.  Or, to make the customer shopping experience as pleasant as possible.  ("Shopping experience" is a multi-dimensional measure.)

My initial reaction when I read this story was to wonder: had the team heard of Occam's razor?  The most widespread form is "entities must not be multiplied beyond necessity" (entia non sunt multiplicanda praeter necessitatem) which was expressed much later than Occam.  In the O.R. world, it is sometimes expressed as "Use the simplest model that will work".  I wondered whether the effort needed to devise the monitoring systems, modelling process, validate the model and devise a feedback strategy that would work was really necessary.  At first sight, it would not be the simplest model!  In the UK, the feedback often comes from a check-out manager who can call trained staff at any time that the check-outs become busy. 

But, it looks as if the effort has been worth it for Kroger.  The feedback strategy includes a large digital display about the check-outs that is visible to staff and customers, not simply to staff.  As a result, customers report increased satisfaction, because they can see that something is being done.  Whether by accident, or design, check-out staff are now happier (more relaxed?) and have a better interaction with customers.

Will it be good for the bottom line?  Like every commercial enterprise, that is an industrial secret.  But well done to the team at Kroger for taking the problem of supermarket check-out staffing into the 21st century!

Thursday, 26 June 2014

A very public set of queues in series

When our class was introduced to the art and craft of simulation model building, the problem we were given was to model a laundrette.  The reason for this exercise was to study a familiar situation (at least for most students), where there were queues in sequence and non-standard queues as well.  Some customers would use more than one washing machine (one type of server), some would use more than one dryer, some would want both washer and dryer, while others would only use a washer.  The service times on the machines were to all intents and purposes constant, in contrast to the systems we had met in queue theory courses, where an exponential service time was assumed (or in special cases, Gamma or Erlang).  And, if the instructor was especially devious, we would be reminded that this laundrette would not reach a steady state, because the arrival rate of customers was time-dependent.  Our aim in the simulation course was to produce a model and explore the consequences of varying the numbers of washing machines and tumble-dryers.  As I recall, there were various assumptions made about the behaviour of customers who had to queue; generally, it was assumed that every customer would be served.  The doors of the launderette would be closed to customers at a particular moment, but those “inside” would complete their service.  Given the arrival pattern of customers, costs of washes, drying, running the machines and the shop, what would be the best number of each machine to have?

Memories of this exercise came to me when I encountered another everyday situation with queues in sequence and many of the above “features” as well.  I have written earlier about queues in public toilets, and my encounter was in two of these.  Sometime a student project could address the provision of equipment (WCs, urinals, basins, soap dispensers and hand dryers – all “servers” of the sequence of queues) in such facilities, perhaps restricted to those in supermarkets or motorway service stations.  (Just give me the credit for the idea!) 

Many places use a “hole in the wall” which provides soap, water and drying air, either at the press of a button, or automatically in sequence.  One gentlemen’s toilet in Exeter has four urinals, two WCs and two holes in the wall.  Unfortunately, the holes in the wall are programmed to give soap at the press of a button, then 10 seconds of water, followed by 30 seconds of drying air.  Even if a user removes his hands from the orifice, the hot air keeps on coming.  So, the service time at each opening is well over 40 seconds, probably nearer a minute.  It is no wonder that many gentlemen do not bother to use the hand-cleaning machinery.  They would have to queue in the small space, or stand helplessly waiting for the hot air to come to an end so they could start their service.  (It is left as an exercise in human observation to determine how long a male needs to spend at a urinal, and compare that with the time at the hole in the wall.) 

On holiday, I met the opposite extreme; the blast of hot air was a mere four seconds.  Again the user was frustrated, this time at having to repeatedly press a button to get more drying time.  By comparison, one manufacturer claims that their very fast hand dryers take “Only ten seconds”.

So, I suspect that in neither case has anyone considered the implications of the queues and the congestion and frustration caused at each one.  

In contrast, office buildings have to provide facilities according to formulae based on the number of workers in the building – and those formulae have been derived from queue models and (in many cases) simulation.

Wednesday, 25 June 2014

The game of buying a house and stamp duty

My title is an awkward one, I know, and I tried to think of a more punchy headline.

Earlier this year, the average price of a house in the UK reached £250,000.  Now averages in this case do not mean a great deal, as house prices do not follow a Normal (Gaussian) distribution.  But that figure is important, symbolically.  You see, house sales in the UK attract a tax, Stamp Duty Land Tax (SDLT), paid by the buyer as a percentage of the total value paid for the property.  And  SDLT is a cliff-edge tax.  If the transaction is less than £125K, SDLT is 0%.  The next band is up to £250K, and is 1%.  The next band goes to £500K and is 3%, and then is 4% up to £1M, 5% up to £2M and 7% over £2M.  The cliff-edge means that the SDLT on a property costing £250,000 is £2500.  If the property costs one pound more, £250,001, SDLT is £7500.03p.  Hence the importance of reaching that average price.

There are similar cliff-edges at £125K (£0 to £1250), at £500K (£15000 to £20000) and £1M and £2M, but it is the size of the edge at £250K which causes most angst.  Needless to say, there are many ploys of avoiding the jump in SDLT.  It is illegal, for instance to offer £250K for a house and then offer £10K for the bedroom curtains.  Because solicitors are involved with the purchase, they are aware of the need to keep within the law, and ask purchasers to sign documents that confirm that there are no inappropriate side deals involved.  [It is not clear whether one purchaser got away with his offer to pay for the £30,000 wedding of the vendor's daughter to reduce the house price from £520K to £490K and the SDLT from £20800 to £14700.]

All these cliff-edges lead to some strategies for vendors setting the asking price for a property, and for purchasers making offers.  There are very few properties priced close to a cliff-edge threshold.  You won't find many houses with an asking price of £255K.  If you do, then it is probably a sign that the vendor will accept £250K but not a penny less.  In fact, the gap above the cliff-edge is quite large.  Our local paper lists very few between £250K and £280K.  Because of its good economy, Exeter has a vibrant housing market, and our average house prices are very close to £250K (according to one website, over the last year, the mean was £234K, and the rate of increase has pushed it higher).  Over the past year, over fifty houses with an Exeter address sold for exactly £250K, and just 8 sold for between £250,001 and £260,000 ... including one at £253,000.  (The skewness of the house price distribution in Exeter is shown by the observation that of 2367 property sales in the last year, 1714 were under £250K, 2296 under £500K.)

So, the estate agents in Exeter, faced with house prices hovering around the cliff-edge, have to give careful advice about the strategy for pricing. 

But, why did anyone pay £253,000 for a property?  Here is the other side to the situation.  The purchaser also has to devise a strategy.  Many houses are sold by formal or informal tender, and an attractive property may be sold for more than the asking price.  The vendor and agent know this - and it is in their interests to encourage it.  So, what offer does a buyer make for a house listed at £240K, knowing the cliff-edge?  I suspect that the property at £253K was the result of a determined buyer, deciding that he/she really wanted the property, and being prepared to pay the extra £5K tax as part of the deal. The prospective buyer doesn't know how many other bids there will be (unless the agent tells them, nor what bids have been made.)  And the agent and vendor must agree a time to set a deadline for all offers.

I keep wondering how OR could actually help buyers and sellers with property close to one of the cliff-edges.  But I know that OR, through game theory and bidding strategy theory, can offer ways of thinking about the matter.