Systems that are Complex
Classical statistics assume
- Linearity
- Gaussian distributions
- Smooth changes
1. When you have feedback
2. When you have tipping
3. When you have chaos
4. When you have long-tails
5. When you have clusters
6. When you have fractals
- Machine learning
- Genetic algorithms
The noise spikes in SOC systems are called flicker noise, but are actual events, rather than `measurement errors.' Here, usually insignicant events sometimes cause complexity cascades that propagate within a system to produce very large `noise' spikes that appear to us as unexpected events. These cascades are situations where an initially small, and perhaps insignicant-seeming action generates a macro-level event, such as a currency collapse, war, market bubble, riot, bank run, electoral landslide, or a government collapse. - Brunk (2002)
Complexity for Sustainable Development
Science and Policy Summer School
networked systems, incomplete systems, overlapping systems, hierarchical systems
how do we make networks dynamic?
how do we make systems precise?
data analysis, estimators
for research, communication
how do we understand complex drivers?
combining agents and systems and networks
- catastrophe
- data and history
- emergence
- fractal complexity
- drive toward heterogeneity
- Dialogue Wiki Engine
Regressions can be tricked
understanding element and whole
Insights for Sustainable Develelopment
problems of statistical significance
You can't know everything, but knowing nothing tells you a lot.
evolutionary, cross-scale
- non-linearity, chaos
- "state" and evolution
- cybernetics, equifinality, teleology
- structures and feedback
- open systems
- continued dynamics
- Prezi
rank-methods (e.g. copula)
Space, time, and history matter.
A complex system's basic properties are much more likely to be a function of its content than context.
self-organized criticality
Linearity is not innocuous.
Variable errors are ubiquitous
history matters, in societies and ecosystems; you can't get places but by a path
Adaptive Networks
Historical Physics
- linearity
- memoryless
- causality
- unorganized complexity (chance)
- closed systems
- thermodynamic drive to homogeneity
- PowerPoint
spatiality matters, and most interesting systems don't tend toward equilibrium
Not least squres-- L1 norm?
Behavior grows better before it grows worse.
The easy way out usually leads back in.
What are complex systems?
Today's problems come from yesterday's "solutions"
Problems are self-created
Dividing an elephant in half doesn't make two small elephants.
System archetypes
and mental models
When placed in the same system, people, however different, tend to produce similar results
Structure influence behavior
Insights for Sustainable Develelopment
- The computer scientist's dream
- Incomplete work, sloppy thinking
- Dogmatic complexity-mongers
- A focus on techniques
- Ill-defined terms:
Cause and effect are not closely related in time and space.
simplistic approaches,
disconnected from reality
The harder you push, the harder the system pushes back.
The problems with the field
Small changes can produce big results-- but the areas of highest leverate are often the least obvious.
1. Constants, parameters, numbers (subsidies, taxes, standards)
2. Material flows and nodes of material intersection
3. Regulating negative feedback loops
4. Driving positive feedback loops
5. Information flows
6. The rules of the system (incentives, punishments, constraints)
7. The distribution of power over the rules of the system
8. The goals of the system
9. The mindset or paradigm out of which the system– its goals, power structure, rules, its culture– arises
gender, family, evolution
homeostasis and overdeterminism
big models, unverified models
18th c.: integrity of wholes
management, communication, understanding
Sets of elements standing in interaction
isomorphisms between contexts
To start: A caveat
Indications for use
- Complexity science struggles to be distinguished from its methods.
- Agent-based modeling : Complexity :: Econometrics : Economics
- Many courses sadly equate the two.
- Complexity science also involves:
- Models of complexity (SOC, Ising, Network growth)
- Deep insights requiring much more discussion (What "is" complexity?)
non-linear dynamics
non-Gaussian stats
scaling
- Statistical identification/generation of
- chaos
- long-tails
- fractals
- Information theory
- Maximum entropy
- Cellular automata
- Network analysis
- Agent-based modeling
- Cross-scale analysis
- Genetic algorithms
- Machine learning
A catalog of methods
Cartesian space
arbitrary space
>1 decision-maker
>1 scale
innumerable state-space
innumerable solution-space
Alternatives under long-tails
- Take a log, if you can
- Quantile regression (quantreg in R)
- Cauchy or student-t link GLM
- Translate into ranks
Consequences:
- Std. deviation is undefined (maybe mean too).
- More data does not result in closer estimate
- Regression, correlation, ... fail
Easy to detect, if you look:
- Plot distribution of values/residuals
- Look at tails in Q-Q plot
- Small differences lead to big changes
- Easy to produce: feedback and nonlinerity
- Detect by looking at frequencies
Compare the mean to the variance across several samples.
- Random distribution: variance = mean
- Even distribution: low variance for any mean
- Clustered distribution: high variance for any mean
Methods of complexity science
Examples:
- Coastlines and rivers
- Random walks
- Market expectations
- Ecosystem niches
- Economic niches
Random network
How do networks shrink?
Scale-free network
Continually add new vertices
Attach them to nodes based on
current node attachment
Explains:
- Zipf's Laws
- Paper references
- Success-to-successful economics
Preferential attachment model
Scale-free networks
Complex Statistics
- Degree distributions
- Connectedness
- Average distance
- Clustering
Look at how networks grow or shrink.
Few things behave this way.
When is the complexity important?
Networks are a kind of data, like spatial grids.
Only interesting if you can do something with them.
- Influence: connections, average-distance, small-world, communities, eigen-connectivity, ...
- Infection:
Complex Networks
Understanding emergence
- Traditional problems have a small parameter space.
- What if you have an infinite parameter space?
Solving problems
Big models of interactions
Any number of distinctions
Small models of assumptions
ABMs are like analytical models:
- Each agent has a set of rules
- The system as a whole evolves
- Could write out that evolution as a single dynamic equation (in theory)
Good for falsifying theories of emergence
Example model: Zombie apocalypse
Population of agents:
- Each is either infected or not
- Every time a zombie interacts with a non-zombie, there's a probability p that the non-zombie becomes a zombie.
Agent-based model
Analytical Model
- Zombies and non-zombies randomly move to adjacent unoccupied squares.
- If zombie next to non-zombie, consider as interacting.
z is the population of zombies
s is the population of non-zombies
Interaction equation says:
dz / dt = z (p - z)
Sandpiles:
A cellular automata
importance of instability
locally and globally unstable
agent bias and alternatives
build-up and collapse equilibrium
importance of scale, or scaling
endogenous but unpredictable
instability serves self-organized resilience
Insights for Sustainable Development
historical and heterogenous
SOC found in riot and strike growth (Bohstedt and Williams, 1988, Midlarsky, 1978) and urban collapse (Brunk, 2002b, Tainter, 1990).
Model of SOC economy (Brunk 2002)
distributed in space/network
Solow Model
but collapses of nodes can avalanche
Is the process that causes development to fail external to the process of development itself?
SOC
e.g. behavior of a sandpile
Do traps represent too much instability or too little?
but too much instability undermines cooperation (Perry 1995)
Distributed Solow Model
Each firm has individual capital stock, L/N labor, and Cobb-Douglas production
development pushes toward interconnectedness
Growth is "distributed Solow"
and probability of collapse
Every time step, some firms get connections.
Connections increase "technology" (specialization) multiple in production.
When collapse, capital set to 0 and connections severed.
between chaos and order
near threshold of instability
far out of equilibrium
missing information
fractal patches or
scale-free networks
- self-organization support
- critical value support
- collapse facilitation
- critical competition
e.g. sand slope instability
power-law temporal fluctuations
large fluctuations
no "normal size" of events
variance is undefined
scale-independent
unpredictable
Self-organized criticality in SD
society collapse follows a power law (Brunk, 2002)
city size/abundance follows power law (Eeckhout, 2004), corporations too
price fluctuations follow 1/f noise (Pleurou et al, 1999)
Examples of Self-Organized Criticality
Classic examples
Biology and Economy
Are economies SOC?
But not everywhere...
SOC Examples: human-impacted vegetation patterns (Barbier et al, 2006), academic papers (Barabasi and Albert, 1999), market prices (Cootner, 1964), politial popularity (Byers, 1991), war and conflict (Conybeare, 1990)
Price fluctuations in developing countries do not have scale-independence (Matia et al, 2004)
City size distribution differs by country (Soo, 2005, Mulianta et al, 2004)
economic networks are small-world (scale-free?)
evolutionary, path-dependent, multiple equilibria
similar behaviors a many scales (global to personal)
City distribution characteristics, vs. HDI
According to theory, log-log slope for Zipf law is 1.
- High HDI countries have higher power-law slopes (greater decrease in abundance for increase in size)
- High HDI countries more closely approximate a power-law (?)
Data: GapMinder
- 497 indicators
- 259 countries/territories
1. normalized year-to-year differences
2. HDI or
3. sort into bins by HDI deciles
4. estimate PDF by indicator-bin
5. calculate R for log-log regression
Peru's year-to-year indicator differences
- Air accidents killed
- DOTS all new case detection rate (%)
- DOTS new smear-positive case detection rate (%)
- DOTS treatment success (%)
- Lung Female Mortality
- Male 15-64 labour to population (%)
- Male 15+ labour to population (%)
- Male above 15 employment to population (%)
- Neonates protected at birth against neonatal tetanus (PAB) (%)
- Total 15+ labour to population (%)
- Total 25-54 labour to population (%)
- Total expenditure on health as percentage of GDP (gross domestic product)
- Whole country all new case detection rate (%)
- Whole country new smear-positive case detection rate (%)
- 0-4 years- number
- 10-14 years- number
- 15-19 years- number
- 20-39 years- number
- 50+ yrs sex ratio
- Annual population growth rate (%)
- Crude death rate (deaths per 1-000 population)
- DOTS population coverage (%)
- Energe use- total (toe)
- Epidemic affected
- Female 10-14 years (%)
- Female 15-19 years (%)
- Female 20-39 years (%)
- Female 40-59 years (%)
- Flood affected
- Flood killed
- Forest coverage (%)
- HDI
- Income share held by highest 20%
- Lung Male Mortality
- Median age
- Prostate Male Mortality
- Road traffic total deaths
- RTI 0-14 all age adj
- SBP male (mm Hg)- age standardized mean
- Storm affected
- Storm killed
- Surface area (sq. km)
- Total sex ratio
- Water resources: total renewable per capita (actual) (m3/inhab/yr)
- 40-59 years- number
- Crude oil production- total (toe)
- Electricity consumption- total (kWh)
- Fixed broadband Internet subscribers
- GDP per employee- (constant 1990$)
- Homicide 0-14 all age adj
- Hydro production- total (toe)
- Natural Gas Production total (tonnes oil equivalent)
- Per capita government expenditure on health (PPP int. $)
- Per capita government expenditure on health at average exchange rate (US$)
- Per capita total expenditure on health (PPP int. $)
- Population density (per square km)
- Proportion of the population using improved sanitation facilities- total
- Residential electricity consumption- total (kWh)
- Suicide 15-29 all age adj
- Suicide 45-59 all age adj
- Tax revenue (% of GDP)
- TB incidence- all forms in HIV+ (per year)
- Total above 60- number
- Total CO2 emissions from fossil-fuels (metric tons)
- Total water withdrawal per capita (m3/inhab/yr)
- Urban population (% of total)
Moderate SOC (R < .5, > .1)
- 0-14 yrs sex ratio
- 15-24 yrs sex ratio
- 15-49 yrs sex ratio
- Agriculture- value added (% of GDP)
- Arms imports (constant 1990 US$)
- Breast Female Mortality
- Cervix Female Mortality
- Children per woman
- Colon & Rectum Female Mortality
- Colon & Rectum Male Mortality
- Crude birth rate (births per 1000 population)
- Debt servicing costs (% of exports and net income from abroad)
- Female 0-4 years (%)
- Female 15-24 employment to population (%)
- Female 15-64 labour to population (%)
- Female 15+ labour to population (%)
- Female 25-54 labour to population(%)
- Female above 15 employment to population (%)
- General government expenditure on health as percentage of total expenditure on health
- General government expenditure on health as percentage of total government expenditure
- Income per person (PPP) with projections
- Life expectancy at brith
- Male 15-24 employment to population (%)
- Male 65+ labour to population (%)
- Malnutrition prevalence- weight for age (% of children under 5)
- Murdered men- per 100-000- age adjusted
- One-year-olds immunized with three doses of diphtheria tetanus toxoid and pertussis (DTP3) (%)
- Per capita CO2 emissions (metric tons of carbon)
- Private expenditure on health as percentage of total expenditure on health
- Stomach Female Mortality
- Stomach Male Mortality
- Suicide women age adjusted
- Suicide- age adjusted- per 100 000 standard population
- Total 15-24 employment to population (%)
- Total 15-64 labour to population (%)
- Total 65+ labour to population (%)
- Total above 15 employment to population (%)
- Under-five mortality rate
- Agricultural land (% of land area)
- CO2 emissions (kg per 2005 PPP $ of GDP)
- Crude oil production- per capita (toe)
- Electricity consumption- per capita (kWh)
- Energy production- per capita (toe)
- Energy production- total (toe)
- Energy use- per capita (toe)
- Exports of goods and services (% of GDP)
- Exports unit value (index- 2000=100)
- External debt stocks (% of GNI)
- Fixed broadband Internet subscribers (per 100 people)
- Foreign direct investment- net inflows (% of GDP)
- Foreign direct investment- net outflows (% of GDP)
- GDP per capita growth (annual %)
- Gross capital formation (% of GDP)
- High-technology exports (% of manufactured exports)
- Homicide 15-29 all
- Homicide 30-44 all age adj
- Homicide 45-59 all age adj
- Hydro production- per capita (toe)
- Import value index (2000 = 100)
- Imports of goods and services (% of GDP)
- income per person
- Industry- value added (% of GDP)
- Inflation- GDP deflator (annual %)
- Internet users (per 100 people)
- Male 15-19 years (%)
- Male 5-9 years (%)
- Male above 60 (%)
- Merchandise trade (% of GDP)
- Military expenditure (% of GDP)
- Murder per 100-000- age adjusted
- Murdered women- per 100-000- age adjusted
- Natural Gas Production per person (tonnes oil equivalent)
- Net barter terms of trade (2000 = 100)
- Out-of-pocket expenditure as percentage of total health expenditure
- People living with HIV
- Population
- Population growth (annual %)
- Residential electricity consumption- per person (kWh)
- RTI 30-44 all age adj
- RTI 45-59 all age adj
- SBP female (mm Hg)- age standardized mean
- Services- etc.- value added (% of GDP)
- Suicide 0-14 all age adj
- Suicide 30-44 all age adj
- Suicide 60+ all age adj
- TC female (mmol/L)- age standardized mean
- TC male (mmol/L)- age standardized mean
- Total 0-4 years (%)
- Total 15-19 years (%)
- Total 40-59 years (%)
- Total above 60 (%)
- Total GDP (PPP 2005 intl.D)
- Total population both sexes
- Total population female
- Total population male
- Total reserves (% of total external debt)
- Trade balance (current US$)
- Traffic mortality per 100-000- age adjusted
- Traffic mortality women- per 100-000- age adjusted
- Urban population
- Urban population growth (annual %)
- Water resources: total internal renewable per capita (m3/inhab/yr)
Needed more efficiency: model it on a network!
Hydrological model for Himalayan glaciers
integration with climate modeling
- 5-9 years- number
- Adult literacy rate (%). Female
- Adult literacy rate (%). Male
- Adult literacy rate (%). Total
- Agricultural water withdrawal as % of total water withdrawal (%)
- Aid received % of GNI
- Aid received per person (current US$)
- Air accidents affected
- Annual number of AIDS deaths
- Arms exports (constant 1990 US$)
- Births attended by skilled health staff (% of total)
- Contraceptive prevalence (% of women ages 15-49)
- Democracy score
- Dependency ratio
- Drought affected
- Epidemic killed
- Estimated ART Coverage (CD4 < 350)
- Estimated HIV Prevalence% - (Ages 15-49)
- Estimated new births
- Estimated new HIV infections (All ages)
- External debt stocks- total (DOD- current US$)
- Female 5-9 years (%)
- Female 65+ labour to population (%)
- Female above 60 (%)
- Forest area (sq. km)
- GINI index
- Homicide 60+ all age adj
- Income share held by fourth 20%
- Income share held by highest 10%
- Income share held by lowest 10%
- Income share held by lowest 20%
- Income share held by second 20%
- Income share held by third 20%
- Industrial water withdrawal as % of total water withdrawal (%)
- Infant Mortality Rate
- Male 0-4 years (%)
- Male 10-14 years (%)
- Male 20-39 years (%)
- Male 25-54 labour to population (%)
- Male 40-59 years (%)
- Mobile cellular subscriptions (per 100 people)
- Mobile cellular subscriptions- total number
- Municipal water withdrawal as % of total withdrawal (%)
- Municipal water withdrawal per capita (m3/inhab/yr)
- New and relapse cases
- New and relapse cases (per 100 000 population)
- New smear-positive cases (per 100 000 population)
- One-year-olds immunized with MCV (%)
- One-year-olds immunized with three doses of Hepatitis B (HepB3) (%)
- PC per 100
- Per capita total expenditure on health at average exchange rate (US$)
- Personal computers
- Population in urban agglomerations of more than 1 million (% of total population)
- Poverty headcount ratio at $1.25 a day (PPP) (% of population)
- Poverty headcount ratio at $2 a day (PPP) (% of population)
- Proportion of the population using improved drinking water sources- rural
- Proportion of the population using improved drinking water sources- total
- Proportion of the population using improved drinking water sources- urban
- Proportion of the population using improved sanitation facilities- rural
- Proportion of the population using improved sanitation facilities- urban
- Reported Cases
- Reported cases per 100000
- Reported Deaths
- Reported Deaths per 100000
- Roads- paved (% of total roads)
- RTI 15-29 all age adj
- RTI 60+ all age adj
- Stillbirth rate
- Suicide among men- per 100 000- age adjusted
- TB incidence- all forms (per 100 000 population per year)
- TB incidence- all forms in HIV+ (per 100 000 population per year)
- TB incidence- smear-positive (per 100 000 population per year)
- TB mortality- all forms (per 100 000 population per year)
- TB mortality- all forms in HIV+ (per 100 000 population per year)
- TB mortality- all forms in HIV+ (per year)
- TB prevalence- all forms (per 100 000 population per year)
- TB prevalence- all forms in HIV+ (per 100 000 population per year)
- TB prevalence- all forms in HIV+ (per year)
- Total 10-14 years (%)
- Total 20-39 years (%)
- Total 5-9 years (%)
- Total fertility rate
- Total water withdrawal (summed by sector) (10^9 m3/yr)
- Trade balance (% of GDP)
- Traffic mortality men- per 100-000- age adjusted
- Under 5 mortality rate from CMEinfo
- Youth literacy rate (%). Female
- Youth literacy rate (%). Male
- Youth literacy rate (%). Total
memetic propogation of models
Want to explore SOC: model it on a network!
Expanded Solow-model for poverty traps
Extras
- intractable, systemic problems
- spatially heterogenous
Challenges:
- Language of model building
- model visualization
- Modular simulation
Challenges:
- new handling of feedback
- how to adjust parameters
- how to determine hierarchical allotments
- missing models fail gracefully
Reasons:
- research platform
- better models
- communication tool
Reasons:
- incomplete, hierarchical, interacting
Open Interfaces
Overlapping Models
Applications
The future of modeling for SusDev
6
3
rebound and border leakage
Challenges:
- conceptualizing components that work along different networks
- what about when not available?
- Systems Regression
- Driving forces simplifier
- Tipping point finder
- Model evaluation
Reasons:
- Different stocks flow differently
- Deaggregating through networks
- Capture society's network properties
Why bigger models?
Computational Tools
- Precision? Debatable.
- Accuracy? Better.
- As a platform? If popular.
Multiple Network Maps
Finding tipping points for change
5
groundwater use, fishery management
2
environmental degradation
Challenges:
- what of endogenous dynamics
- data library (contextual, incomplete)
Challenges:
- how to allow systems to vary
- how to ensure matches aggregate
Reasons:
- callibration and validation
- defining flows
Integrating Data
Reasons:
- spatial heterogeneity
- finer tipping points
Combining systems and space
4
1
systems: intelligent objects
Technical Details
Challenges and Steps Forward