Understanding Distance:
Moving from Local Search toNationwide Search
Xavier Sánchez Loro

15/6/2022

Understanding Distance: Moving from Local Search to Nationwide Search

Outline1.

What's Wallapop?

2.

The beginnings: Local search

3.

Next generation: Nationwide search

4.

Know your domain: Distance sensitivity

5.

a.

Contextb.

Experiments

Conclusion

Understanding Distance: Moving from Local Search to Nationwide Search

What's Wallapop?

3Understanding Distance: Moving from Local Search to Nationwide Search

Wallapop in Numbers
15M monthly users

Biggest 2nd-hand andunique goods virtual
marketplace in Spain+180M articles have found a second
homePresence also in Italy

46% of all transactions are completedwith Wallapop Envíos (shippingservices)
90% Mobile users

4Understanding Distance: Moving from Local Search to Nationwide Search

Wallapop started as a local marketplace in 2013●●

Most transactions happened locally, face 2 face.
Search was also local (showing nearby items ﬁrst insearch results)

In 2021 we introduced nationwide search with more focus
on textual matching and less on distance.
●●Good for Wallapop (shipping adoption) and for someusers (opening more opportunities to discover uniquecatalog)
But many users still prefer local sales in some cases.

5Understanding Distance: Moving from Local Search to Nationwide Search

Wallapop Catalog
Characteristics

6Understanding Distance: Moving from Local Search to Nationwide Search

Catalog characteristics
Several tens of millions of products
Hundreds of thousands of new(unique) products uploaded daily● Several tens of millions of products● Hundreds of thousands of new products uploaded daily
Highly volatile user generatedcontent● Highly volatile content● GeolocatedGeolocated● Wide array of product categories○ Consumer Goods
Wide array of product categories○ CarsConsumer Goods○ Real EstateCars○ Fashion
Real Estate● Support for shipping products nationwide and cross-border
FashionSupport for shipping products
nationwide and cross-border7

Understanding Distance: Moving from Local Search to Nationwide Search

Catalog characteristics

Catalog Volatility

Hundreds of thousands of new
Several tens of millions of products(unique) listings per day!
Hundreds of thousands of new(unique) products uploaded daily
Survival bias: best items are● Several tens ofsoldmillionsof products
quickly(recency is an
importantofrankingfactor) uploaded daily● Hundreds of thousands
new products
Highly volatile user generatedcontent● Highly volatile content
Very sparse feedback per listing● GeolocatedAggregations by product-id are
Geolocated● Wide array of productcategories
not so useful○ Consumer Goods
Wide array of product categories○ CarsConsumer Goods○ Real EstateCars○ Fashion
Real Estate● Support for shipping products nationwide and cross-border
FashionSupport for shipping products
nationwide and cross-border
8Understanding Distance: Moving from Local Search to Nationwide Search

Catalog characteristics

Catalog Volatility

User Generated
Content

Hundreds of thousands of new
Several tens of millions of products(unique) listings per day!
Hundreds of thousands of new
Inconsistent quality ofimages and text (typos,(unique) products uploaded daily
Survival bias: best items areambiguity, keyword stuﬃng,● Several tens ofsold
millionsofproducts
quickly (recency is an
importantofrankingfactor) uploaded daily etc..)● Hundreds of thousands
new products
Highly volatile user generated
content
Unstructured listings (few
● Highly volatile contentVery sparse feedback per listingattributes)● GeolocatedAggregations
byproduct-idareGeolocated● Wide array of productcategories
In many products, image
not so usefultells more than text
○ Consumer Goods
Wide array of product categories○ CarsConsumer Goods○ Real EstateCars○ Fashion
Real Estate● Support for shipping products nationwide and cross-border
FashionSupport for shipping products
nationwide and cross-border9Understanding Distance: Moving from Local Search to Nationwide Search

The beginnings:local search10Understanding Distance: Moving from Local Search to Nationwide SearchLocal search characteristics
Each user sees items around them based on their location
Not strict distance sorting
Applying relevance per distance areas
Allows having the feeling of sorting by distance but allows
to implement more sophisticated relevance per areas

11Understanding Distance: Moving from Local Search to Nationwide Search

Local search characteristics
Visibility of products is distributed according to geolocation of
the product uploaded and where buyer is searching
Products has less competition to be visible in their area for acertain keyword
Topicality of the item is traded-oﬀ for locality and recency

12Understanding Distance: Moving from Local Search to Nationwide Search

Local search insights
Works really well for some users and product types
Relevance of the item is biased towards location○ Topicality suﬀers○ Highly relevant (and shippable) content is not shown
to the user
Very useful for building a strong local community
Not boosting transactional services adoption

13Understanding Distance: Moving from Local Search to Nationwide Search

Next generation:nationwide (andcross-border)
search14

Understanding Distance: Moving from Local Search to Nationwide SearchSearch in all the country
Increase product visibility range
Increase competition between products“good” shippable products sell faster“bad” products are penalised
Reduced number of items soldIncreased number of shipping transactions
Some categories and type of products are
better ﬁtted for local search15Understanding Distance: Moving from Local Search to Nationwide Search

Search in all the country

Several experiments
onlineIncrease product visibility range
Increase competition between products“good” shippable products sell faster“bad” products are penalised

Varying the impact of locationand distanceWith no distance as ranking
factorReduced number of items soldWith distance as ranking factor
Increased number of shipping transactions
Some categories and type of products are
better ﬁtted for local searchContent grouped by location andinterleaved

16Understanding Distance: Moving from Local Search to Nationwide Search

Search in all the country

Several experiments
onlineIncrease product visibility range
Increase competition between products“good” shippable products sell faster“bad” products are penalised

Varying the impact of locationand distanceWith no distance as ranking
factorReduced number of items soldWith distance as ranking factor
Increased number of shipping transactions
Some categories and type of products are
better ﬁtted for local searchContent grouped by location andinterleaved

Users still don’t see thesame listing
Less variance on results
per user than in local
search17

Understanding Distance: Moving from Local Search to Nationwide Search

The diﬀerent variants have basically very similar performance, with a better balance for variant
with distance as ranking factor

18

Understanding Distance: Moving from Local Search to Nationwide Search

The diﬀerent variants have basically very similar performance, with a better balance for variant
with distance as ranking factor+24% in shippingtransactions

19

Understanding Distance: Moving from Local Search to Nationwide Search

The diﬀerent variants have basically very similar performance, with a better balance for variant
with distance as ranking factor+24% in shippingtransactions-17% in local sales-3 % items sold20

Understanding Distance: Moving from Local Search to Nationwide Search

The diﬀerent variants have basically very similar performance, with a better balance for variant
with distance as ranking factor+24% in shippingtransactions+2,2% CTR

-17% in local sales-3 % items sold21

Understanding Distance: Moving from Local Search to Nationwide Search

The diﬀerent variants have basically very similar performance, with a better balance for variant
with distance as ranking factor+24% in shippingtransactions+2,2% CTR

Lower clicks positions,buyers click more on
top-ranked items.

-17% in local sales-3 % items sold22

Understanding Distance: Moving from Local Search to Nationwide Search

The diﬀerent variants have basically very similar performance, with a better balance for variant
with distance as ranking factor+24% in shippingtransactions-17% in local sales-3 % items sold

+2,2% CTR

Lower clicks positions,buyers click more on
top-ranked items.
-5.5% Total chatdecreased

23

Understanding Distance: Moving from Local Search to Nationwide Search

The diﬀerent variants have basically very similar performance, with a better balance for variant
with distance as ranking factor+24% in shippingtransactions-17% in local sales-3 % items sold

+2,2% CTR

Lower clicks positions,buyers click more on
top-ranked items.
-5.5% Total chatdecreased

30% of relevancesearches had thedistance ﬁlter appliedor the order changed todistanceDiﬀerent behaviour
between Recurrent andNew users
Retention rate is not
aﬀected24

Understanding Distance: Moving from Local Search to Nationwide Search

Know yourdomain: Distancesensitivity

25

Understanding Distance: Moving from Local Search to Nationwide Search

From local search to relevance
Local search & local
transactions
Relevance search &shipped transactions

We want the best of both worlds!
26

Understanding Distance: Moving from Local Search to Nationwide Search

We saw diﬀerent level of sensitivity to distance27

Understanding Distance: Moving from Local Search to Nationwide Search

We saw diﬀerent level of sensitivity to distanceSome queries convert locally (bicicleta, iphone, sofa),some of them don’t (records, pokemon cards, books, etc..)

28

Understanding Distance: Moving from Local Search to Nationwide Search

We saw diﬀerent level of sensitivity to distance

Related to product type/Query sensitivity

Category + Subcategory

Some queries convert locally (bicicleta, iphone, sofa),some of them don’t (records, pokemon cards, books, etc..)

Keyword29

Understanding Distance: Moving from Local Search to Nationwide Search

We saw diﬀerent level of sensitivity to distance

Related to product type/Query sensitivity

Category + Subcategory

Some queries convert locally (bicicleta, iphone, sofa),some of them don’t (records, pokemon cards, books, etc..)

KeywordUsers in big cities convert more locally
Users countryside convert at larger distances30

Understanding Distance: Moving from Local Search to Nationwide SearchWe saw diﬀerent level of sensitivity to distance

Related to product type/Query sensitivity

Category + Subcategory

Some queries convert locally (bicicleta, iphone, sofa),some of them don’t (records, pokemon cards, books, etc..)

Keyword
Location

Users in big cities convert more locally
Users countryside convert at larger distances31Understanding Distance: Moving from Local Search to Nationwide Search

We saw diﬀerent level of sensitivity to distance

Related to product type/Query sensitivity

Category + Subcategory

Some queries convert locally (bicicleta, iphone, sofa),some of them don’t (records, pokemon cards, books, etc..)

Keyword
Location

Users in big cities convert more locally
Users countryside convert at larger distances

Non shippable items have very low conversions on longdistances32Understanding Distance: Moving from Local Search to Nationwide Search

We saw diﬀerent level of sensitivity to distance

Related to product type/Query sensitivity

Category + Subcategory

Some queries convert locally (bicicleta, iphone, sofa),some of them don’t (records, pokemon cards, books, etc..)

KeywordLocation

Users in big cities convert more locally
Users countryside convert at larger distances

Item shippability

Non shippable items have very low conversions on longdistances

33

Understanding Distance: Moving from Local Search to Nationwide SearchDistance
sensitivity
experiments

34

Understanding Distance: Moving from Local Search to Nationwide Search

Nationwide search is the baseline35Understanding Distance: Moving from Local Search to Nationwide Search

Nationwide search is the baseline

Query sensitivity: we adapt the importance of distancedepending on the query36

Understanding Distance: Moving from Local Search to Nationwide Search

Nationwide search is the baseline

Query sensitivity: we adapt the importance of distancedepending on the querybicicleta

warhammer

37

Understanding Distance: Moving from Local Search to Nationwide Search

Nationwide search is the baseline

Query sensitivity: we adapt the importance of distancedepending on the querybicicleta

Categories and subcategories that cannot be shipped use
local searchwarhammer

38

Understanding Distance: Moving from Local Search to Nationwide Search

Nationwide search is the baseline

Query sensitivity: we adapt the importance of distancedepending on the querybicicleta

Categories and subcategories that cannot be shipped use
local search

Detection of keywords that are distance sensitive
Several methods tested for keyword extraction

warhammer

39

Understanding Distance: Moving from Local Search to Nationwide Search

Nationwide search is the baseline

Query sensitivity: we adapt the importance of distancedepending on the querybicicleta

Categories and subcategories that cannot be shipped use
local search

Detection of keywords that are distance sensitive
Several methods tested for keyword extraction

Switch to local searchEasy to test

warhammer

Aggressive option40Understanding Distance: Moving from Local Search to Nationwide Search

Nationwide search is the baseline

Query sensitivity: we adapt the importance of distancedepending on the querybicicleta

Categories and subcategories that cannot be shipped use
local search

Detection of keywords that are distance sensitive
Several methods tested for keyword extraction

Switch to local search
Easy to test
Aggressive option

Deﬁne areas of sensitivity todistance and adapt ranking forthemwarhammer

Sensible
Not sensible
41Understanding Distance: Moving from Local Search to Nationwide SearchDistance
sensitivity
experiments:
switching to localsearch42Understanding Distance: Moving from Local Search to Nationwide Search

Hypothesis
By changing to local search ona considerable amount of
distance-sensitive queries webelieve we would be able tohave a higher impact on
searches that will translate inmore total sold items

Variants description
A - Baseline: current behavior
B - Variant: distance sensitivity
10k queries

43Understanding Distance: Moving from Local Search to Nationwide Search

10k queries impactChangeGeneral impact

ChangePrimary Goal

Total Sold Items+6,65 %

Primary Goal

Total Sold Items+1,21 %

Secondary Goal

Local Sold Items+8,80 %

Secondary Goal

Local Sold Items+1,70 %

Health Metric

TRX with Shipping-18,81 %Health Metric

TRX with Shipping0%

Health MetricChats+7,55 %

Health MetricChats+0,87 %

44

Understanding Distance: Moving from Local Search to Nationwide Search

2nd iteration

Variants description
A - Baseline: current behavior

Increase keyword coverage
Adapt keyword selection

B - Variant: distance sensitivity
10k queries
C - Variant: distance sensitivity
110k queries

45Understanding Distance: Moving from Local Search to Nationwide Search

Change vs B

Change vs C

Primary Goal

Sold Items+1,1%+3,8%Secondary Goal

Purchase Intention+0,7%+2,2%

Health MetricLocal Sold Items+1,5%+6,9%

Health Metric

TRX with Shipping

-0,3%

-3,2%

46

Understanding Distance: Moving from Local Search to Nationwide SearchDistance sensitivity
experiments:
adapting area size(without locationdimension)
47

Understanding Distance: Moving from Local Search to Nationwide Search

Variants description
Hypothesis
By ﬁne-tuning results basedon query and distancesensitivity area size we believethat users will ﬁnd moremeaningful results and we will
increase total transactions

A - Baseline: relevance by default, we don’t
use any ﬁle
B - Variant 1: Distance sensitive queries,
based on transaction data in normal space(km)
C - Variant 2 : Distance sensitive queries,
based on transaction data in logarithm space(km)
D - Variant 3 : Distance sensitive queries,
based on chat/ship data in normal space
(km)

48

Understanding Distance: Moving from Local Search to Nationwide Search

Change V1

Change V2

Change V3

Primary Goal

Sold Items+1.68%+2.48%+1.62%

Secondary Goal

Purchase Intention+1.69%+2.84%+1.89%

Health Metric

Local Sold Items+4.76%+9.14%+5.20%

Health Metric

TRX with Shipping-1.83%-4.97%-2.51%

49

Understanding Distance: Moving from Local Search to Nationwide SearchDistance sensitivity
experiments:
adapting area size
(adding locationdimension)
50

Understanding Distance: Moving from Local Search to Nationwide Search51Understanding Distance: Moving from Local Search to Nationwide SearchHypothesis
By considering search queryand search location webelieve that users will ﬁnd
more meaningful results andwe will increase totaltransactions without heavily
penalising shipped
transactions

Variants description
A - Baseline: Distance sensitive queries,
based on transaction data in normal space(km)
B - Variant 1: Distance sensitive queries andlocation sensitivity score
C - Variant 2 : Distance sensitive queries (80percentile radius) and location sensitivityscore52

Understanding Distance: Moving from Local Search to Nationwide Search

Change V1

Change V2

Primary Goal

Sold Items-1,30%-0,82%

Secondary Goal

Purchase Intention-0,96%-0,55%

Health Metric

Local Sold Items-2,34%-1,49%

Health Metric

TRX with Shipping-012%-0,04%

53

Understanding Distance: Moving from Local Search to Nationwide SearchDistance
sensitivity
experiments: itemshippability
54

Understanding Distance: Moving from Local Search to Nationwide Search

We see that above certain threshold most oftransactions happen on shippable items…
… but with nationwide we show ‘a lot’ of
non-shippable items over long distances55

Understanding Distance: Moving from Local Search to Nationwide Search

Hypothesis
By considering item
shippability we believe thatusers will ﬁnd moremeaningful results and we will
increase total transactions
increasing shipped
transactions without damaging
local transactions

Variants description
A - Baseline: Distance sensitive queries,
based on transaction data in normal
space (km)B - Variant 1: Penalize non-shippable
items above median transaction kms56

Understanding Distance: Moving from Local Search to Nationwide Search

Change V1

Primary Goal

Sold Items+1,14%

Secondary Goal

Purchase Intention-1,81%

Health MetricLocal Sold Items-1,05%

Health MetricTRX with Shipping+3,51%

57

Conclusions

Understanding Distance: Moving from Local Search to Nationwide Search

Know your domain
Which ranking factors arecore to your users
Identify and iterate them

Balancing user and business
needs

Reduce defects generated by yourrelevance algorithm

What is good for the businessmight not be ideal for the user

Impossible to address all thepossible issues, corner cases
Understand at which level you
should deal with your key factors

59

Thank you!